Production and use of a premium fuel grade petroleum coke

ABSTRACT

A premium “fuel-grade” petroleum coke is produced by modifying petroleum coking technology. Coking process parameters are controlled to consistently produce petroleum coke within a predetermined range for volatile combustible material (VCM) content. The invention includes a process of producing a coke fuel, the method comprising steps: (a) obtaining a coke precursor material derived from crude oil and having a volatile organic component; and (b) subjecting the coke precursor material to a thermal cracking process for sufficient time and at sufficient temperature and under sufficient pressure so as to produce a coke product having volatile combustible materials (VCMs) present in an amount in the range of from about 13% to about 50% by weight. Most preferably, the volatile combustible materials in the coke product typically may be in the range of from about 15% to about 30% by weight. The present invention also provides methods for (1) altering the coke crystalline structure, (2) improving the quality of the coke VCM, and (3) reducing the concentration of coke contaminants. Fuels made from the inventive coke product and methods of producing energy through the combustion of such fuels are also included. Finally, novel environmental control techniques are developed to take optimal advantage of the unique characteristics of this upgraded petroleum coke.

[0001] This application is a continuation-in-part of U.S. applicationSer. No. 09/556,132, filed Apr. 21, 2000, which claimed the benefit ofInternational Application No. PCT/US99/19091, filed Aug. 20, 1999, whichclaimed the benefit of U.S. application Ser. No. 09/137,283, filed Aug.20, 1998, now U.S. Pat. No. 6,168,709.

[0002] This application is also a continuation-in-part of U.S.application Ser. No. 09/763,282, filed Feb. 20, 2001, which claimed thebenefit of International Application No. PCT/US99/19091, filed Aug. 20,1999, which claimed the benefit of U.S. application Ser. No. 09/137,283,filed Aug. 20, 1998, now U.S. Pat. No. 6,168,709.

[0003] The entirety of each of the above priority documents is herebyincorporated by reference.

BACKGROUND OF THE INVENTION

[0004] 1. Field of the Invention

[0005] This invention relates generally to the field of petroleum cokingprocesses, and more specifically to modifications of petroleum cokingprocesses for the production of a premium-quality, “fuel-grade”petroleum coke. This invention also relates generally to the use of thisnew formulation of petroleum coke for the production of energy, and morespecifically to modifications in conventional, solid-fuel furnaces andenvironmental control systems to take optimal advantage of its uniqueproperties.

[0006] 2. Description of Prior Art

[0007] Since initial efforts to refine crude oil in the U.S. during thelate 1800s, the search for an appropriate use for the heaviest fractionsof crude oil (i.e. the “bottom of the barrel”) has been a perplexingproblem. Initially, many refineries received little to no value from theheaviest fractions of crude oil. Some were noted to simply discard the“bottom of the barrel.” Over time, some of the heavy crude oil fractionswere used in asphalt products and residual fuel oils. However, thedemand for these products was not sufficient to consume increasingproduction.

[0008] As demand for transportation fuels (e.g. gasoline, diesel, andaviation fuels) increased in the early 1900s, thermal cracking processeswere developed to convert the heavy crude oil fractions into lighterproducts. These refinery processes evolved into the modern cokingprocesses that predominate the technology currently used to upgrade theheaviest fractions of the crude oil. These processes typically reducethe quantity of heavy oil fractions, but still produce unwantedby-products (e.g. petroleum coke) with marginal value.

[0009] A. Production of Petroleum Coke; Coking Processes

[0010] In general, modern coking processes employ high-severity, thermaldecomposition (or “cracking”) to maximize the conversion of very heavy,low-value residuum feeds to lower boiling hydrocarbon products. Cokerfeedstocks typically consist of non-volatile, asphaltic and aromaticmaterials with “theoretical” boiling points exceeding 1000° F. atatmospheric pressure. The boiling points are “theoretical” because thesematerials coke or crack from thermal decomposition before they reachsuch temperatures.

[0011] Coking feedstocks normally consist of refinery process streamswhich cannot economically be further distilled, catalytically cracked,or otherwise processed to make fuel-grade blend streams. Typically,these materials are not suitable for catalytic operations because ofcatalyst fouling and/or deactivation by ash and metals. Common cokingfeedstocks include atmospheric distillation residuum, vacuumdistillation residuum, catalytic cracker residual oils, hydrocrackerresidual oils, and residual oils from other refinery units.Consequently, coking feedstocks vary substantially among refineries.Their composition and quantity primarily depend on (1) the input crudeoil blend, (2) refinery processing equipment, and (3) the optimizedoperation plan for any particular refinery. In addition, contaminantcompounds, which occur naturally in the crude oil, generally haverelatively high boiling points and relatively complex molecularstructures. Consequently, these contaminant compounds, containing sulfurand heavy metals, tend to concentrate in these residua. Many of theworst process streams in the refinery have become coker feedstock, andtheir contaminants usually end up in the petroleum coke by-product. Forthis reason, the coking processes have often been labeled as the“garbage can” of the refinery.

[0012] There are three major types of modern coking processes currentlyused in refineries to convert the heavy crude oil fractions into lighterhydrocarbons and petroleum coke: Delayed Coking, Fluid Cokin™, andFlexicoking™. In all three of these coking processes, the petroleum cokeis considered a by-product that is tolerated in the interest of morecomplete conversion of refinery residues to lighter hydrocarboncompounds, referred to as “cracked liquids” throughout this discussion.These cracked liquids range from pentanes to complex hydrocarbons withboiling ranges typically between 350 and 950° F. The heavier crackedliquids (e.g. gas oils) are commonly used as feedstocks for furtherrefinery processing that transforms them into transportation fuel blendstocks.

[0013] The delayed coking process has evolved with many improvementssince the mid-1930s. Essentially, delayed coking is a semi-continuousprocess in which the heavy feedstock is heated to a high temperature(between 900° F. and 1000° F.) and transferred to large coking drums.Sufficient residence time is provided in the coking drums to allow thethermal cracking and coking reactions to proceed to completion. Theheavy residua feed is thermally cracked in the drum to produce lighterhydrocarbons and solid, petroleum coke. One of the initial patents forthis technology (U.S. Pat. No. 1,831,719) discloses “The hot vapormixture from the vapor phase cracking operation is, with advantage,introduced into the coking receptacle before its temperature falls below950° F., or better 1050° F., and usually it is, with advantage,introduced into the coking receptacle at the maximum possibletemperature.” The “maximum possible temperature” in the coke drum favorsthe cracking of the heavy residua, but is limited by the initiation ofcoking in the heater and downstream feed lines, as well as excessivecracking of hydrocarbon vapors to gases (butane and lighter). When otheroperational variables are held constant, the “maximum possibletemperature” normally minimizes the volatile material remaining in thepetroleum coke by-product. In delayed coking, the lower limit ofvolatile material in the petroleum coke is usually determined by thecoke hardness. That is, petroleum coke with <8 wt. % volatile materialsis normally so hard that the drilling time in the decoking cycle isextended beyond reason. Various petroleum coke uses have specificationsthat require the volatile content of the petroleum coke by-product to be<12%. Consequently, the volatile material in the petroleum cokeby-product typically has a target range of 8-12 wt. %. Prior art in thedelayed coking process, including recent developments, has attempted tomaximize the production of cracked liquids with less coke production. Inthis manner, the prior art of delayed coking has attempted to minimizecoke yield and the amount of volatile materials it contains.

[0014] Fluid Coking™, developed since the late 1950s, is a continuouscoking process that uses fluidized solids to increase the conversion ofcoking feedstocks to cracked liquids, and further reduce the volatilecontent of the product coke. In Fluid Coking™, the coking feedstockblend is sprayed into a fluidized bed of hot, fine coke particles in thereactor. Since the heat for the endothermic cracking reactions issupplied locally by these hot particles, this permits the cracking andcoking reactions to be conducted at higher temperatures (about 480-565°C. or 900-1050° F.) and shorter contact times than in delayed coking.Roughly 15-25% of the coke is burned in an adjacent burner vessel inorder to create the hot coke nuclei to contact the feed in the reactorvessel, and satisfy the process heat requirements. The Fluid Coking™technology effectively removes the lower limit of volatile content inthe petroleum coke, associated with delayed coking. The volatile contentof the petroleum coke produced by the Fluid Coking™ technology istypically minimized (or reduced), within the range of 4-10 wt. %.Consequently, the quantity of petroleum coke, produced by a givenfeedstock, and its volatile content are significantly reduced in theFluid Coking™ technology (vs. delayed coking).

[0015] Flexicoking™ is an improvement of the Fluid Coking™ process, inwhich a third major vessel is added to gasify the product coke. A cokingreactor, a heater (vs. burner) vessel, and a gasifier are integratedinto a common fluidized-solids circulating system. The “cold coke” fromthe reactor is partially devolatilized in the heater vessel. In thegasifier, over 95% of the gross product coke is gasified to produceeither low heating-value fuel gas or synthesis gas to make liquid fuelsor chemicals. In this manner, the net coke yield is substantiallyreduced. The purge coke (˜5% of the product coke) from the Flexicokin™process normally contains about 99% of the feed metals and has avolatile content of 2-7 wt. %.

[0016] Through the years, improvements in the coking processes have beensubstantially devoted to increasing the yield and recovery of crackedliquids and decreasing the coke yield. Thus, the content of volatilematerial in the resulting petroleum coke has been continually decreased,where possible. Various patents disclose improvements to the delayedcoking process that include, but are not limited to, (1) coker designsthat reduce drum pressures (e.g. 25 to 15 psig), (2) coker designs toprovide virtually no recycle, and (3) periodic onstream spalling ofheaters to increase firing capabilities and run length at higher heateroutlet temperatures. These technology advances have been implemented inan effort to maximize the cracked liquid yields of the delayed coker andreduce petroleum coke yields and volatile content.

[0017] Other modifications of these coking processes introduce variouswastes for disposal. Several patents disclose various means to injectcertain types of oily sludges. Other prior art uses these cokingprocesses for the disposal of used lubricating oils. Additional patentsdisclose the use of these coking processes for the disposal of otherwastes. In general, these patents discuss the potential limited impacton the coke yield and volatile content, and promote other means tonegate any increases. Also, these waste disposal techniques oftenincrease the ash content of the coke and can introduce additional,undesirable impurities, such as sodium. Consequently, the objectives ofthese patents are to reuse or dispose of these wastes rather thanenhance the petroleum coke properties.

[0018] B. Uses of Petroleum Coke

[0019] The uses of the petroleum coke by-products from these cokingprocesses depend primarily on its (1) physical properties and (2)chemical composition (i.e. degree of contamination). The physicalproperties (density, crystalline structure, etc.) of the petroleum cokeby-product are determined by various factors, including coking feedstockblend, coking process and operation, and volatile content of the coke.The chemical composition and degree of contamination of the petroleumcoke is primarily determined by the composition of the coking feedstockblend. That is, most of the contaminant compounds (e.g. sulfur,nitrogen, and various metals) in the petroleum coke by-product come fromheavy, complex chemical structures in the coking feedstocks, whichnormally come from the refinery's crude oil blend. Conversely, thecontaminants in the refinery's crude oil blend ultimately concentrate inthe petroleum coke. Consequently, light, sweet crudes generally haveless contaminants and allow the production of higher value petroleumcoke by-products. However, crude oils are becoming increasingly heavyand sour, increasing the production of low-grade petroleum coke.

[0020] Premium and intermediate grades of petroleum cokes have low tomoderate levels of sulfur (e.g. 0.5-2.5%) and heavy metals (vanadium,nickel, etc.). These grades of coke have various uses as electrodes andmetallurgical carbon in the production of aluminum and steel. In someapplications, the raw petroleum coke is further processed by calciningto remove volatile material and increase the coke density. Petroleumcoke that cannot meet the required specifications of these higher-valuemarkets is classified as “fuel-grade” petroleum coke. As such, thispoorest grade of petroleum coke typically has high concentrations ofsulfur (2.5-5+wt. %) and/or heavy metals, including vanadium and nickel.

[0021] “Fuel-grade” petroleum coke is actually a misnomer. Thetraditional “fuel-grade” petroleum coke actually performs very poorly asa fuel. First of all, traditional “fuel-grade” petroleum coke cannotsustain self-combustion due to its poor fuel properties and combustioncharacteristics. Secondly, its high sulfur content (e.g., >2.5 wt. %)creates substantial environmental problems, particularly in the UnitedStates. Thirdly, high concentrations of certain metals can be precursorsfor post-combustion, liquid salts that deposit on heat transfersurfaces, reducing efficiency and/or causing accelerated corrosion.Finally, high concentrations of sulfur and/or metals can detrimentallyeffect product quality, when used as fuel directly in chemical processes(e.g. concrete kilns). Consequently, traditional “fuel-grade” petroleumcoke can only be used in conventional furnaces when combined with otherfuels (often requiring separate fuel processing and management systems).Alternatively, specially designed combustion systems, that arecumbersome and expensive, can use this coke as fuel. Until thesedeficiencies are addressed, the traditional “fuel-grade” petroleum cokewill continue to be a very low value product. In fact, traditional“fuel-grade” petroleum coke could be classified as a hazardous waste inthe United States, if its value continues its downward trend andrefiners receive no sales value as a product. In this scenario, costs ofhazardous waste disposal could dramatically reduce refineryprofitability, and cause the shutdown of many refineries across theUnited States.

[0022] Numerous technologies were apparently developed to modify cokingfeedstocks and produce petroleum coke of sufficient quality for non-fueluses of higher value. Many patents disclose various technologies forremoving or diluting certain undesirable contaminants in the petroleumcoke. As such, they go far beyond the degree of decontamination that isrequired for petroleum coke used as a fuel. Accordingly, simplerapproaches that are less expensive and less complicated are desirablefor the lower level of decontamination required for petroleum coke usedas a fuel.

[0023] Various combustion technologies have been developed to overcomethe deficiencies in “fuel-grade” coke, but no prior art successfullyaddresses these problems by upgrading the coke via the coking process.The prior art has failed to upgrade the quality of “fuel-grade”petroleum coke sufficiently to use in conventional, solid-fuelcombustion systems (e.g. high heat capacity furnaces with suspensionburners firing pulverized fuel, such as coal). Specially designedcombustion systems (noted above) include fluidized bed combustion,pyrolysis/gasification systems, and low heat capacity furnaces (i.e.without heat absorption surfaces). In general, these systems arecumbersome, expensive, and have significant problems in scaling sizeupward. Several patents also disclose technologies to grind andstabilize coke/oil mixtures for use in conventional combustion systems.However, the quality of the traditional petroleum coke used in thesefuel mixtures normally limits (1) the particle size distribution of thesolids and (2) the degree of combustion (i.e. carbon burnout).

[0024] In summary, prior art does not address the major problemsassociated with traditional “fuel-grade” petroleum coke:

[0025] 1. There remains a major need to produce “fuel-grade” petroleumcoke that is able to sustain self-combustion with acceptable combustionefficiencies.

[0026] 2. Secondly, no known prior art satisfactorily resolves theproblems associated with the formation of sticky, corrosive salts in thecombustion process, due to certain contaminants in the petroleum coke.

[0027] 3. Finally, prior art does exist for the desulfurization anddemetallization of petroleum coke, but it is complicated and expensive.Simpler approaches are needed for the lower level of decontaminationrequired for petroleum coke used as a fuel.

OBJECTS AND ADVANTAGES OF THE INVENTION

[0028] Accordingly, it is one object of the present invention to providea petroleum coke fuel that is able to (1) sustain self-combustion withacceptable combustion efficiencies, (2) sufficiently reduce thecorrosive ash deposits harmful to the combustion system, and/or (3)reduce the need for complicated and expensive coke decontaminationprocesses and environmental control systems, including elaboratepollution control equipment in the combustion system. Other objects andadvantages of the present invention will be readily apparent from thefollowing descriptions of the drawings and exemplary embodiments.

[0029] The present invention successfully addresses the problemsassociated with traditional “fuel-grade” petroleum coke, which othertechnologies have failed to do. This invention provides the followingunique features that produce new and unexpected results:

[0030] 1) Modifications in the coking process provide the ability tocontrol the quantity and quality of volatile combustible material (%VCM) in the petroleum coke.

[0031] Acceptable levels of porous, combustible carbon residue in theproduct coke (related to the crystalline structure of the coke) are alsoassured by these and further modifications. Consequently, the presentinvention produces a petroleum coke that is capable of self-combustion.That is, the upgraded petroleum coke can be successfully burned inconventional, solid-fuel furnace systems without auxiliary fuel or theneed to mix with other fuels.

[0032] 2) Process modifications reduce quantities of certain salt andmetal contaminants to acceptable levels in the petroleum coke. Thesemodifications address potentially problematic combustion products(sticky, corrosive salts) that deposit on downstream heat exchange andpollution control equipment.

[0033] 3) Combustion process modifications address high sulfur levels inthe petroleum coke that are environmentally prohibitive. Complicated andexpensive desulfurization technologies of the prior art are not requiredfor petroleum coke decontamination. These modest combustion processmodifications offer a simpler approach to the control of sulfur oxideand particulate emissions. Similar process modifications (furtherembodiments of this invention) can provide the opportunity to reduceother flue gas emissions, including nitrogen oxides, carbon dioxide, airtoxics, etc. In this manner, the optimal reductions in particulates,sulfur oxides, and other undesirable flue gas components can beachieved.

[0034] 1. Utility of the Invention

[0035] The present invention provides a superior “fuel-grade” petroleumcoke for many solid-fuel and/or chemical feedstock applications whileimproving overall operations, maintenance, and profitability in the oilrefinery.

[0036] The present invention provides the means to control theconcentrations of volatile combustible material, crystalline structure,and undesirable contaminants in a manner that produces a premium,fuel-grade petroleum coke. This upgraded petroleum coke has qualitiesthat make it superior to the traditional “fuel-grade” petroleum coke,various types of coals, and other solid fuels. In most solid fuelapplications, these improved characteristics provide potential usersbetter combustion, higher energy efficiency, substantially improvedpollution control, and significantly lower operating and maintenancecosts. Alternatively, this premium fuel-grade coke can be partiallyoxidized via gasification processes to provide chemical feedstocks orlow-quality, gaseous fuels.

[0037] The present invention produces a high-value product from the“bottom of the barrel” for many refineries. The present invention isalso less sensitive (compared to prior art) to undesirable contaminantsin the crude oil mixture being processed by a typical refinery.Consequently, the present invention improves the flexibility to processvarious crudes, including low-cost crudes, that are heavy, sour and/orcontain high levels of metals or asphaltenes. As the world supplies oflight, sweet crude decreases, this benefit has greater utility, sincemuch greater quantities of “fuel-grade” coke will be produced from theremaining heavy, sour crude oils. In addition, the process modificationsof this invention are expected to (1) improve operation and maintenanceof the coker process, (2) potentially increase coker and refinerythroughput, and (3) improve other refinery operations. All of thesefactors potentially improve the overall refinery profitability.

[0038] Further objects and advantages of this invention will becomeapparent from consideration of the drawings and ensuing descriptions.

SUMMARY OF THE INVENTION

[0039] It has been discovered that an upgraded petroleum coke can havemuch better fuel properties and combustion characteristics than coalswith significantly higher (or comparable) levels of volatile combustiblematerials (VCM). In addition, the unique characteristics of thisupgraded petroleum coke create the opportunity for applications of novelenvironmental control technologies to meet or exceed environmentalrequirements. Surprisingly, these novel and unexpected results can beproduced with modest modifications to the existing coking processes andcombustion systems. However, both the production and use of this newformulation of petroleum coke are contrary to conventional wisdom andcurrent trends in the petroleum coking processes and solid fuelcombustion systems.

[0040] 1. Coking Processes

[0041] Conventional wisdom and current trends in the petroleum cokingprocesses focus on coking designs and operations that (1) maximize theproduction and recovery of cracked liquid hydrocarbons and (2) minimizethe level of volatile combustible material in the resulting coke. Incontrast, the modified coking process of the present invention givespriority to producing a petroleum coke with consistently higher volatilecombustible material of sufficient quality for self-combustion. Thismodified process also promotes a coke crystalline structure that is moreconducive to good combustion. In many cases, low-level decontaminationof the petroleum coke to acceptable levels is also achieved to eliminate(or reduce) the formation of corrosive ash deposits in the combustionprocess. Surprisingly, the present invention, in all its embodiments,can produce a premium, “fuel-grade” petroleum coke, capable ofself-combustion with superior fuel properties and combustioncharacteristics, while decreasing cracked liquid conversion efficiencyby <10% (preferably <1%). The present invention discusses various meansto offset (or limit) the loss of cracked liquid yield. In certainsituations, the present invention can upgrade the petroleum coke fuel,while actually increasing overall cracked liquids production, due topotential increases in coker and/or refinery throughput.

[0042] In general terms, the invention includes a process of producing acoke fuel, the method comprising steps: (a) obtaining a coke precursormaterial derived from crude oil, and having a volatile organiccomponent; and (b) subjecting the coke precursor material to a thermalcracking process for sufficient time and at sufficient temperature andunder sufficient pressure so as to produce a coke product having avolatile combustible material (VCM) present in an amount in the range offrom about 13% to about 50% by weight. Most preferably, the volatilecombustible material in the coke product typically may be in the rangeof from about 15% to about 30% by weight. The thermal cracking processof the present invention may include a process selected from the groupconsisting of delayed coking processes and Fluid Coking™ processes. Asused herein, “volatile combustible material” (VCM) is defined by ASTMMethod D 3175. In the present invention, all the VCM is contained in thecoke precursor material derived from crude oil or added to the cokingprocess; as contrasted with any substantial volatile organic component(e.g. fuel oil) that has been added to a coke product after the cokingprocess is complete.

[0043] In some cases, a consistently higher VCM level will be all thatis necessary to provide petroleum coke capable of self-combustion.Process controls of the prior art typically minimize VCM in theby-product petroleum coke. That is, coking units in the prior arttypically have operational setpoints to produce by-product petroleumcoke with VCM levels below 12%. In contrast, the present inventiondiscusses various means to increase and consistently maintain highercoke VCM levels for various coking processes, including delayed andFluid Coking™ processes. A “minimum acceptable” VCM specification(e.g. >15% VCM) is discussed as an exemplary means of maintainingproduct quality.

[0044] In many cases, altering the petroleum coke crystalline structurewill also be required to produce petroleum coke capable ofself-combustion. In most (but not all) cases, altering the crystallinestructure will enhance combustion characteristics and reduce the“minimum-acceptable” VCM specification. The present invention discussesvarious means to promote favorable coke crystalline structure. In anexemplary embodiment, the coker process changes that increase andconsistently maintain the desired VCM level also promote greaterproduction of the more desirable sponge coke (vs. shot coke or needlecoke). That is, the organic compounds, creating the higher VCM in thecoke, are expected to alter the coke formation mechanisms (i.e. thermalvs. asphaltic coke) to favor sponge coke production. The sponge cokecrystalline structure is preferable due to higher porosity and softness,which greatly improve its combustion characteristics. Furtherembodiments are provided to inhibit the formation of undesirable dense,spherical coke, called “shot coke.” Consequently, the present inventionpromotes sponge coke crystalline structure that favors good combustionand maintains acceptable levels of shot coke . A “minimum-acceptable”sponge coke specification is discussed as one means of maintaining cokecrystalline quality. That is, process control methods will consistentlyachieve a coke crystalline structure that preferably contains 40-100%sponge coke (vs. shot coke); most preferably 60-100% sponge coke (vs.shot coke). Alternatively, a “maximum-acceptable” shot cokespecification or a specification for average coke density (e.g. gm/cc)can provide alternative measures for process control of a particularcoker design and feedstock.

[0045] In other cases, the addition of higher quality VCM (e.g. VCM withboiling points of about 250-850° F. and heating values of 16-20,000Btu/lb) may be necessary to produce petroleum coke capable ofself-combustion. Alternatively, higher quality VCM in the petroleum cokecan be used to reduce the overall VCM specification (i.e.minimum-acceptable VCM). The present invention discusses various meansto add higher quality VCM within the coking process, and achieve uniformintegration within the coke. In this manner, a softer coke crystallinestructure with higher porosity is maintained, while further improvingthe upgraded coke's combustion characteristics.

[0046] In many (but not all) cases, low-level decontamination of thepetroleum coke may be necessary to assure acceptable levels of sulfur,sodium, and other metals for the combustion process. In an exemplaryembodiment, the coke precursor material is subjected to an efficientdesalting process prior to the thermal cracking process to reduce theconcentration of certain undesirable contaminants in the upgradedpetroleum coke. An exemplary desalting method uses three stages ofconventional, refinery desalting processes. Alternatively, filtration,catalytic, and other efficient desalting methods can be used. Any ofthese desalting processes will remove various contaminants to variousdegrees. However, sodium is the contaminant of primary concern toprevent problematic ash products (e.g. sticky, corrosive salts) from thecombustion of most “fuel-grade” petroleum coke. The coke precursormaterial preferably will contain less than 15 ppm by weight sodium, andmost preferably less than 5 ppm by weight sodium. Further embodiments ofthe present invention describe other means for achieving sodium, sulfur,and metals decontamination objectives noted above. Desulfurization anddemetallization embodiments are discussed as alternatives to enhanceenvironmental control options and also improve the prevention ofproblematic ash products.

[0047] 2. Solid Fuel Combustion Systems

[0048] Conventional wisdom and current trends of solid-fuel combustionsystems are moving toward further use of traditional, “fuel-grade”petroleum coke as (1) a periodic “spiking” fuel, (2) continual use incoal/coke fuel blends, or (3) primary fuel in complex, speciallydesigned combustion systems. In the first two cases, traditionalpetroleum coke typically makes up less than 20% of the blend and oftenrequires a separate fuel preparation system. In contrast, the presentinvention produces a Premium “Fuel-Grade” Petroleum Coke that has greatvalue as a replacement for various solid fuels, including numerouscoals. The primary use is expected to be a direct replacement of variouscoals in existing coal-fired boilers (utility, industrial, orotherwise). That is, the present invention includes a new formulation ofcoke product made in accordance with a process according to the presentinvention, in all of its embodiments. The present invention alsoincludes a method for producing energy, the method comprising generallycombusting a fuel, the fuel comprising coke, the coke comprisingvolatile combustible material (VCM) in an amount in the range from about13% to about 50% by weight. Preferably, the volatile combustiblematerial in the coke is in the range from about 15% to about 30% byweight.

[0049] A method of the present invention also includes a method ofproducing energy using a fuel that comprises mixtures of the upgradedcoke of the present invention, and other fuels, including coke and solidfuels (e.g. coal), or coke and liquid fuels (e.g. fuel oil), or coke andgaseous fuels (e.g. natural gas) or any combination of these; andpreferably consisting essentially of the upgraded coke of the presentinvention as described herein. Where the coke is mixed with coal, it maybe preferred that the weight ratio of coke to coal in said mixture begreater than about 1:4. Alternatively, the method of producing energy inaccordance with the present invention may feature a heat release rate ofthe coke in such a fuel mixture greater than 20%. However, it may bepreferred that the fuel comprises the upgraded coke including volatilecombustible material in an amount in the range from about 13% to about50% by weight, most preferably in the range of about 15% to about 30% byweight. Consequently, the method of the present invention allows for theachievement of optimal combustion properties while also allowing thecontrol of costs.

[0050] Conventional wisdom and current trends of environmental controlsfor solid-fuel combustion systems is moving toward (1) low-sulfur energysources (solid-fuels and otherwise), (2) extensive system modificationsto add complex, expensive environmental controls, and (3) repoweringconversions to alternative energy technologies with lower environmentalemissions. Many coal-fired, utility boilers have been switched tolow-sulfur coal to comply with the first phase of acid rain controlprovisions under the Clean Air Act Amendments of 1990. Complex,expensive environmental controls and repowering options are beingevaluated for compliance in Phase 2.

[0051] In contrast, the method of the present invention may optionallyand preferably include a method for producing energy, as described, anda method for removing sulfur oxides and/or other undesirable componentsfrom its flue gas. The present invention uses novel techniques to burnthe premium, “fuel-grade” petroleum coke with higher sulfur content andobtain lower sulfur oxide emissions. The unique properties of theupgraded petroleum coke allow it to be used as the primary fuel inexisting, pulverized coal boilers. In most cases, use of the upgradedpetroleum coke as the primary fuel, unleashes >90% of the capacity inthe existing particulate control device (PCD), due to its much lower ashcontent. In these applications, the existing particulate control devicescan be readily converted to emissions control systems that providesufficient control of sulfur oxides (SOx), carbon dioxide, nitrogenoxides (NOx), air toxics, and/or other undesirable flue gas components.The method for removing undesirable components (1) converts theundesirable components to collectible particulates upstream of theexisting PCD and (2) collects such particulates in the existingparticulate control device. That is, the method of the present inventionfor producing energy further includes a method for removing undesirableflue gas components. This method generally comprises (1) an injection ofconversion reagents with sufficient mixing and sufficient residence timeat sufficient temperature to convert undesirable flue gas components tocollectible particulates upstream of a particulate control device (PCD)and (2) collecting said particulates in particulate control device, saidparticulate control device includes, but is not limited to, a PCDprocess selected from the group consisting of electrostaticprecipitators (dry or wet), filtration, cyclones, and conventional wetscrubbers.

[0052] In one embodiment, the unreacted conversion reagents of this fluegas conversion process can be effectively recycled to increase reagentutilization and performance. The recycle rate preferably exceeds 5% byweight of the collected flyash. This level of reagent recycle is aunique feature of this flue gas conversion process, due to the fuelproperties and combustion characteristics of the upgraded coke.

[0053] In another embodiment, the spent flue gas conversion reagents canbe regenerated and reused. The regeneration rate can exceed 70% byweight of the collected flyash, and preferably less than 30% of thecollected fly ash is disposed as a purge (or blowdown) stream,containing high concentrations of impurities. The regeneration methodincludes, but is not limited to, a process selected from the group ofhydration, precipitation, and other unit operations. The purge streamcan be used as a resource for valuable metals, which are extracted andpurified. This type of reagent regeneration can (1) substantiallydecrease reagent make-up requirements and costs, (2) dramatically reduceflyash disposal and costs, (3) reduce CO₂ emissions, (4) create aresource for valuable metals, and (5) provide the means to economicallyimprove the flue gas conversion process via the use of more reactivereagents. The regeneration of conversion reagents is a unique feature ofthis flue gas conversion process, due to the fuel properties and thecombustion characteristics of the upgraded coke.

[0054] For SOx removal, the flue gas conversion process of the presentinvention is similar to dry sorbent injection and dry scrubbertechnologies, but has novel improvements due to the unique properties ofthe upgraded petroleum coke of the present invention. In addition to therecycling and regeneration of reagents noted above, these novelimprovements include increased reagent reactivity, improved reagentutilization, shorter residence times, and greater opportunity forsalable products. All of these improvements over the prior art increaseSOx removal efficiencies and reduce costs.

[0055] The present invention also discusses embodiments to integrateand/or optimize various environmental control techniques. The flue gasconversion process may be used in coordination with traditional wet ordry SOx scrubbing systems to improve or optimize control of variousundesirable flue gas components. Also, upgraded cokes with low sulfurcontent (e.g. sweet crude feedstocks, coker feedstock desulfurization,etc.) can provide greater flexibility in the use of the available PCDcapacity (i.e. other than SOx). Furthermore, the integration ofactivated coke technology is also discussed for the combined control ofSOx, NOx, carbon dioxide and air toxics.

[0056] In the practical application of the present invention, theoptimal combination of methods and embodiments will vary significantly.That is, site-specific, design and operational parameters of theparticular coking process and refinery must be properly considered.These factors include (but should not be limited to) coker design, cokerfeedstocks, and effects of other refinery operations. In addition,site-specific, design and operational parameters of the particularsolid-fuel combustion system and its environmental controls must beproperly considered. These factors include (but should not be limitedto) combustion system design, current fuel characteristics, design ofenvironmental controls, and environmental requirements. Consequently,case-by-case analyses (often including pilot plant tests) are requiredto address site-specific differences in the optimal application of thepresent invention. The present invention discusses methods to optimizethe production and use of the upgraded petroleum coke for eachparticular application.

BRIEF DESCRIPTION OF DRAWINGS

[0057]FIG. 1 shows a basic process flow diagram for key elements of atraditional delayed coking process.

[0058]FIG. 2 shows a basic process flow diagram for a conventional,coal-fired utility boiler with traditional particulate control device(PCD): Baghouse, electrostatic precipitator (ESP), or other. In thiscase, the combustion system has been modified to include reactionvessel(s) and/or reagent injection system(s) for control of undesirableflue gas components.

[0059]FIG. 3 shows comparisons of burning profiles for existing coalsand traditional petroleum coke.

[0060]FIG. 4 shows a basic process flow diagram for key elements of atraditional Fluid Coking™ process.

[0061]FIG. 5 shows a basic process flow diagram for a conventional,coal-fired utility boiler with a wet scrubber downstream of thetraditional particulate control device (PCD): Baghouse, electrostaticprecipitator (ESP), or other. The combustion system has been modified toinclude a reaction vessel(s) and/or reagent injection system(s) forcontrol of undesirable flue gas components.

[0062]FIG. 6A shows a cross sectional view of an exemplary basicequipment diagram of a coke drum having a side-draw vapor line whereinthe coke drum is adapted for injection of certain media to thermallyquench the vapors exiting the coke drum during the coking cycle of thedelayed coking process. The existing coke drum(s) have been modifiedwith reinforced flanges for quench media lances that can be removed formaintenance, as needed.

[0063]FIG. 6B shows a partial top plan view of the coke drum of FIG. 6A.

[0064]FIG. 6C shows a cross sectional view of an exemplary basicequipment diagram of a coke drum having a center-draw vapor line whereinthe coke drum is adapted for injection of certain media to thermallyquench the vapors exiting the coke drum during the coking cycle of thedelayed coking process. The existing coke drum(s) have been modifiedwith reinforced flanges for quench media lances that can be removed formaintenance, as needed.

[0065]FIG. 6D shows a partial top plan view of the coke drum of FIG. 6C.

[0066]FIG. 6E shows a cross sectional view of an exemplary basicequipment diagram of a coke drum having a side-draw vapor line whereinthe coke drum is adapted for injection of certain media via a verticalspray in the vapor line to thermally quench the vapors exiting the cokedrum during the coking cycle of the delayed coking process.

[0067]FIG. 6F shows a partial top plan view of the coke drum of FIG. 6E.

[0068]FIG. 6G shows a cross sectional view of an exemplary basicequipment diagram of a coke drum having a side-draw vapor line whereinthe coke drum is adapted for injection of certain media via a horizontalspray in the vapor line to thermally quench the vapors exiting the cokedrum during the coking cycle of the delayed coking process.

[0069]FIG. 6H shows a partial top plan view of the coke drum of FIG. 6G.

[0070]FIG. 7A shows a cross sectional view of a basic equipment diagramfor a modified drill stem to inject media that thermally and/orchemically quenches excessive cracking reactions in the vapor phaseduring the coking cycle of the delayed coking process. This equipmentmay serve the purpose of quenching heavy vapors exiting the coke drum ina manner similar to the equipment in FIGS. 6A through 6H. The existingdrill stem, coke drum derrick, and coke drum center flange have beenmodified for injection of certain agents in the coking cycle, whilemaintaining the ability to use the existing drill stem to cut coke fromthe drum in the decoking cycle.

[0071]FIG. 7B shows a cross sectional view of an exemplary sealing.mechanism (i.e., an internal double mechanical seal) for the modifiedhead flange of FIG. 7A in this high-pressure operation.

[0072]FIG. 8 shows an exemplary process flow diagram for a delayedcoking system with three coke drums. This delayed coker has beenmodified to provide three process cycles: coking, coke treatment, anddecoking cycles. The coke quench is completed during the last twocycles.

[0073]FIG. 9 shows an exemplary operating conditions diagram forpetroleum coke hydroprocessing. Three zones of different operatingapproaches are demonstrated.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENT(S)

[0074] In view of the foregoing summary, the following presents adetailed description of the exemplary embodiments of the presentinvention, currently considered the best mode of practicing the presentinvention. The discussion of the exemplary embodiments is divided intotwo major subjects: (1) the production of premium “fuel-grade” petroleumcoke in a modified delayed coking process, and (2) the use of thispetroleum coke in conventional, pulverized-coal (PC) utility boilers.Example I is provided at the end of this discussion to illustrate anexemplary embodiment of the present invention.

[0075] 1. Production of Premium “Fuel-Grade” Petroleum Coke: ModifiedDelayed Coking Process

[0076] The discussion of the production of premium, “fuel-grade”petroleum coke in a modified delayed coking process is divided into thefollowing topics: (a) traditional delayed coking: process description,(b) process control of the prior art, (c) coke formation mechanisms andvarious crystalline structures, (d) volatile combustible materials (VCM)in the petroleum coke, (e) process control of the present invention (VCMand crystalline structure), (f) low-level decontamination of cokerfeedstocks: 3-stage desalting operation, and (g) impacts of the presentinvention on refinery operations.

[0077] A. Traditional Delayed Coking: Process Description

[0078]FIG. 1 is a basic process flow diagram for the traditional delayedcoking process of the prior art. The delayed coking process equipmentfor the present invention is essentially the same, but the operation, asdiscussed below, is substantially different. Delayed coking is asemi-continuous process with parallel coking drums that alternatebetween coking and decoking cycles.

[0079] In the coking cycle, coker feedstock is heated and transferred tothe coke drum until full. Hot residua feed 10 is introduced into thebottom of a coker fractionator 12, where it combines with condensedrecycle. This mixture 14 is pumped through a coker heater 16, where thedesired coking temperature (normally between 900° F. and 950° F.) isachieved, causing partial vaporization and mild cracking. Steam orboiler feedwater 18 is often injected into the heater tubes to preventthe coking of feed in the furnace. Typically, the heater outlettemperature is controlled by a temperature gauge 20 that sends a signalto a control valve 22 to regulate the amount of fuel 24 to the heater. Avapor-liquid mixture 26 exits the heater, and a control valve 27 divertsit to a coking drum 28. Sufficient residence time is provided in thecoking drum to allow the thermal cracking and coking reactions toproceed to completion. By design, the coking reactions are “delayed”until the heater charge reaches the coke drums. In this manner, thevapor-liquid mixture is thermally cracked in the drum to produce lighterhydrocarbons, which vaporize and exit the coke drum. The drum vapor linetemperature 29 (i.e. temperature of the vapors leaving the coke drum) isthe measured parameter used to represent the average drum temperature.Petroleum coke and some residuals (e.g. cracked hydrocarbons) remain inthe coke drum. When the coking drum is sufficiently full of coke, thecoking cycle ends. The heater outlet charge is then switched from thefirst coke drum to a parallel coke drum to initiate its coking cycle.Meanwhile, the decoking cycle begins in the first coke drum.

[0080] In the decoking cycle, the contents of the coking drum are cooleddown, remaining volatile hydrocarbons are removed, the coke is drilledfrom the drum, and the coking drum is prepared for the next cokingcycle. Cooling the coke normally occurs in three distinct stages. In thefirst stage, the coke is cooled and stripped by steam or other strippingmedia 30 to economically maximize the removal of recoverablehydrocarbons entrained or otherwise remaining in the coke. In the secondstage of cooling, water or other cooling media 32 is injected to reducethe drum temperature while avoiding thermal shock to the coke drum.Vaporized water from this cooling media further promotes the removal ofadditional vaporizable hydrocarbons. In the final cooling stage, thedrum is quenched by water or other quenching media 34 to rapidly lowerthe drum temperatures to conditions favorable for safe coke removal.After the quenching is complete, the bottom and top heads of the drumare removed. The petroleum coke 36 is then cut, typically by hydraulicwater jet, and removed from the drum. After coke removal, the drumheadsare replaced, the drum is preheated, and otherwise readied for the nextcoking cycle.

[0081] Lighter hydrocarbons 38 are vaporized, removed overhead from thecoking drums, and transferred to a coker fractionator 12, where they areseparated and recovered. Coker heavy gas oil (HGO) 40 and coker lightgas oil (LGO) 42 are drawn off the fractionator at the desired boilingtemperature ranges: HGO: roughly 650-870° F; LGO: roughly 400-650° F.The fractionator overhead stream, coker wet gas 44, goes to a separator46, where it is separated into dry gas 48, water 50, and unstablenaphtha 52. A reflux fraction 54 is often returned to the fractionator.

[0082] In general, delayed coking is an endothermic reaction with thefurnace supplying the necessary heat to complete the coking reaction inthe coke drum. The exact mechanism of delayed coking is so complex thatit is not possible to determine all the various chemical reactions thatoccur, but three distinct steps take place:

[0083] 1. Partial vaporization and mild cracking of the feed as itpasses through the furnace

[0084] 2. Cracking of the vapor as it passes through the coke drum

[0085] 3. Successive cracking and polymerization of the heavy liquidtrapped in the drum until it is converted to vapor and coke

[0086] B. Process Control of the Prior Art

[0087] In traditional delayed coking, the optimal coker operatingconditions have evolved through the years, based on much experience anda better understanding of the delayed coking process. Operatingconditions have normally been set to maximize (or increase) theefficiency of feedstock conversion to cracked liquid products, includinglight and heavy coker gas oils. More recently, however, the cokers insome refineries have been changed to maximize (or increase) cokerthroughput. In both types of operation, the quality of the byproductpetroleum coke is a relatively minor concern. In “fuel-grade” cokeoperations, either mode of operation detrimentally affects the fuelproperties and combustion characteristics of the coke, particularly VCMcontent and crystalline structure.

[0088] In general, the target operating conditions in a traditionaldelayed coker depend on the composition of the coker feedstocks, otherrefinery operations, and coker design. Relative to other refineryprocesses, the delayed coker operating conditions are heavily dependenton the feedstock blends, which vary greatly among refineries (due tovarying crude blends and processing scenarios). The desired cokerproducts and their required specifications also depend greatly on otherprocess operations in the particular refinery. That is, downstreamprocessing of the coker liquid products typically upgrades them totransportation fuel components. The target operating conditions arenormally established by linear programming (LP) models that optimize theparticular refinery's operations. These LP models typically useempirical data generated by a series of coker pilot plant studies. Inturn, each pilot plant study is designed to simulate the particularrefinery's coker design. Appropriate operating conditions are determinedfor a particular feedstock blend and particular product specificationsset by the downstream processing requirements. The series of pilot plantstudies are typically designed to produce empirical data for operatingconditions with variations in feedstock blends and liquid productspecification requirements. Consequently, the coker designs and targetoperating conditions vary significantly among refineries.

[0089] In common operational modes, various operational variables aremonitored and controlled to achieve the desired delayed coker operation.The primary independent variables are feed quality, heater outlettemperature, coke drum pressure, and fractionator hat temperature. Theprimary dependent variables are the recycle ratio, the coking cycle timeand the drum vapor line temperature. The following target control rangesare normally maintained during the coking cycle for these primaryoperating conditions:

[0090] 1. Heater outlet temperatures in the range of about 900° F. toabout 950° F.,

[0091] 2. Coke drum pressure in the range of about 15 psig to 100 psig:typically 20-30 psig,

[0092] 3. Hat Temperature in the range of 650-720° F: typically 670 to700° F.

[0093] 4. Recycle Ratio in the range of 0-100%; typically 10-20%,

[0094] 5. Coking cycle time in the range of about 15 to 24 hours;typically 18-24 hours, and a

[0095] 6. Drum Vapor Line Temperature 50 to 100° F. less than the heateroutlet temperature: range 825 to 880° F.; typically 830 to 860° F.

[0096] These traditional operating variables have primarily been used tocontrol the quality of the cracked liquids and various yields ofproducts, with minor attention to controlling the respective compositionof the by-product petroleum coke. Throughout this discussion, “crackedliquids” refers to hydrocarbon products of the coking process that have5 or more carbon atoms. They typically have boiling ranges between 97and 870° F, and are liquids at standard conditions. Most of thesehydrocarbon products are valuable transportation fuel blendingcomponents or feedstocks for further refinery processing. Consequently,cracked liquids are normally the primary objective of the cokingprocess.

[0097] Since the mid-1930s, better understanding of the delayed cokingprocess and technological advances have continually maximized (orincreased) the efficiency of feedstock conversion. Feedstock conversionis often cited as liquid yield (i.e. barrel of cracked liquid productper barrel of feed). Increasing the yield of cracked liquids isgenerally accomplished by changing the operating conditions to affect(1) the balance between cracking and coking reactions and/or (2) thevaporization and recovery of the cracked liquid products. Though thespecific operating conditions vary among refineries, the following rulesof thumb have been noted as guidelines for reductions in coke yield, andassociated increases in the yield of cracked liquids:

[0098] 1. Each 10° F. increase in coke-drum vapor line temperaturereduces coke yield on feed by 0.8 wt. % and increases gas anddistillates by 1.1 volume% on feed

[0099] 2. Each 8 psi reduction in the coke drum pressure reduces thecoke yield on feed by 1.0 wt. % and increases liquid yield by 1.3 volume% on feed

[0100] 3. Reducing the recycle by 10 vol.% on feed reduces the cokeyield by 1.2 wt. % on feed and increases the liquid plus gas yield by1.0 vol.% onfeed

[0101] 4. Reducing the virgin gas oil content of the coker feed by 10%reduces coke yield by 1.5 wt. %

[0102] Technology advances have also been implemented in the effort tomaximize the liquid yields of the delayed coker. These include, but arenot limited to, (1) coker designs to reduce drum pressure to 15 psig,(2) coker designs to provide virtually no recycle, and (3) periodiconstream spalling of heaters to increase firing capabilities and runlength at higher heater outlet temperatures.

[0103] Over the past ten years, some refineries have switched cokeroperating conditions to maximize (or increase) the coker throughput,instead of maximum efficiency of feedstock conversion to crackedliquids. Due to processing heavier crude blends, refineries often reacha limit in coking throughput that limits (or bottlenecks) the refinerythroughput. In order to eliminate this bottleneck, refiners often changethe coker operating conditions to maximize (or increase) cokerthroughput in one of two ways:

[0104] 1. If the coker is fractionator (or vapor) limited, increase thedrum pressure (e.g., 20 to 25 psig.)

[0105] 2. If the coker is drum (or coke make) limited, reduce cokingcycle time (e.g., 20 to 16 hours)

[0106] Both of these operational changes increase the coker throughput.Though either type of higher throughput operation reduces the efficiencyof feedstock conversion to cracked liquids (i.e. per barrel of feedbasis), it often maximizes (or increases) the overall quantity (i.e.barrels) of cracked liquids produced. These operational changes alsotend to increase coke yield and coke VCM, as noted previously. However,any increase in drum pressure or decrease in coker cycle time is usuallyaccompanied by a commensurate increase in heater outlet and drum vaporline temperatures to offset (or limit) any increases in coke yield orVCM.

[0107] The current trend in delayed coking includes capital improvementsto the original coker design to eliminate bottlenecks and maximize (orincrease) both Coker liquid yields and coker throughput, to the extentpossible. Limits on coke heaters, coke drums, and fractionators areremoved by employing equipment modifications that incorporate technologyadvancements. These modifications will normally address the refinery'sprojected coker feedstock composition and quantity. The timing of thesemodifications is likely to depend on many factors, including (1)justification via the loss of cracked liquids to increased coke yields,and (2) the refinery's capital investment criteria (e.g., alternativeprojects and higher operational risk factors, such as increasedenvironmental regulations).

[0108] In both types of process control in the prior art, the VCMcontent of the byproduct coke is used mostly as a post-mortem gauge ofsuccessful operation, NOT as an essential operational variable. The cokeVCM is measured after the batch operation is complete. Pilot plantstudies are used to predict the coke VCM for a particular set ofoperating conditions, feedstock, and coker design. However, thescaled-up commercial operation may stray from target VCM levels, due toless than ideal conditions. If needed, adjustments in operatingconditions are usually made based on experience for future cokingbatches. Typically, the target operating range for coke VCM in delayedcoking is 8-12 wt. %. If the coke VCM is lower than 8 wt. %, the coke isusually too hard to cut from the drum within the normal decoking cycletime. A coke VCM greater than 12 wt. % is normally considered poorconversion efficiency. Also, some grades of anode and needle coke have amaximum VCM product specification (typically <12 wt. %) that assuresproper density characteristics. Accordingly, the normal operatingconditions for both maximum conversion and maximum throughput modes arecontinually modified to achieve the lowest possible coke VCM in thelong-term, with acceptable coker operation. Consequently, the processcontrol options of the prior art detrimentally impact the fuelproperties and combustion characteristics of “fuel-grade” coke. That is,the coke VCM content and/or crystalline structure of the by-product cokeare not normally sufficient to sustain self-combustion.

[0109] Delayed coker process controls of the prior art (i.e. maximumconversion and/or maximum throughput) also tend to promote theproduction of undesirable coke crystalline structure. These operatingconditions typically promote the formation of shot coke, particularlyfor heavy feedstocks. In some refineries, sponge coke can predominateshot coke. However, the sponge coke in this shot/sponge coke blend willtend to have low porosity due to its low VCM. This latter outcome ismore likely with the operating conditions that maximize cokerthroughput. In either operational mode of the prior art, the byproductcoke tends to have crystalline structures of shot coke and/or spongecoke with low porosity and low VCM. As discussed later, thesecrystalline structures are not desirable for good combustioncharacteristics.

[0110] In conclusion, the operating conditions of the prior art givefirst priority to maximizing the efficiency of feedstock conversion tocracked liquid products or maximizing coker throughput. In either case,the petroleum coke is a byproduct that is tolerated in the interest ofthe maximum production of cracked liquid hydrocarbons, barrel per barrelof feed or total barrels. The VCM content and crystalline structure ofthe resultant coke is a relatively minor concern (by comparison),especially for “fuel-grade” petroleum coke. As such, the process controlof the prior art is not conducive to produce a high-quality,“fuel-grade” coke.

[0111] C. Coke Formation Mechanisms and Various Crystalline Structures

[0112] Coking processes, in general, are high-severity, thermal cracking(or destructive distillation) operations to convert petroleum residuainto distillates, hydrocarbon gases, and coke. The residua feed istypically heated to temperatures exceeding 900° F. Thermal decompositionof the high-molecular, hydrocarbon structures takes place in both theliquid and gaseous phases. The breaking of chemical bonds in the liquidphase typically produces lighter hydrocarbon compounds that vaporizebelow the drum temperature (e.g. <870° F.). The remaining liquids(normally complex hydrocarbon structures with highly aromatic content)polymerize to form coke. Thermal decomposition will continue in thegaseous phase (producing lighter and lighter compounds) until there isnot sufficient activation energy to initiate the endothermic crackingreaction. The cracking and coking reactions occur simultaneously, andtheir degrees of completion primarily depend on the temperature,residence time, and pressure in the reaction system. The remainder ofthis discussion primarily focuses on the thermal cracking of the liquidphase and the subsequent formation of coke.

[0113] The formation of coke in the delayed coking process occursprimarily by two independent coking mechanisms: Thermal Coke andAsphaltic Coke. The thermal coking mechanism is caused by an endothermicreaction: the condensation and polymerization of aromatic compoundscontained in the petroleum residue of the coker feed. This thermal cokemechanism is substantially reduced by operating conditions (e.g. higheroperating temperatures) that increase the production of cracked liquidhydrocarbons. The asphaltic coke mechanism is initiated as solutizingoils are removed by thermal cracking and aromatic cross-linkage from thecoker charge. The large asphaltene and resin molecules precipitate outof solution to form a solid without much change in structure. Theasphaltic coke mechanism (1) is a physical change with no heat ofreaction, (2) is not affected by modified coker operating conditions,and (3) is purely a function of the asphaltene and resin content in thecoker feedstock. The relative degrees of these two coking mechanismshave been noted to determine the crystalline structure of the delayedcoke.

[0114] Petroleum coke from a delayed coker has three major types ofcrystalline structure: needle coke, sponge coke, and shot coke. Needlecoke is formed via virtually all thermal coke mechanism: >95% of thecoke from the condensation and polymerization of aromatics contained ina low-asphaltene coker feedstock (e.g. FCC slurry oil). Sponge coke andshot coke are formed by combinations of thermal and asphaltic cokingmechanisms. When the ratio (R) of asphaltic coke to thermal coke fallsbelow a certain level, sponge coke is formed. Conversely, when R exceedsa certain level, shot coke is formed. This ratio R is difficult tomeasure. Furthermore, the boundary between shot coke and sponge coke isnot definite, but fuzzy, and is expected to vary with coker feedstocks.In fact, the combination of shot coke and sponge coke has been noted toform in the same coking cycle due to temperature variations across thecoke drum. However, limited plant data suggest the crossover point forshot (vs. sponge) coke formation is roughly R>0.7-1.5; preferably 0.8 to1.2.

[0115] D. Volatile Combustible Materials (VCM) in the Petroleum Coke

[0116] Many in the oil refining industry surprisingly believe thatvirtually all of the volatile material in the petroleum coke isvaluable, cracked liquids trapped in the coke. This mistaken beliefapparently occurs due to a major difference in the definition of“volatile materials” for the oil refining industry versus combustionscience. The oil refining industry commonly refers to non-volatile,asphaltic and aromatic materials, contained in the coker feedstocks, as1000 plus materials, which have “theoretical” boiling points exceeding1000 F. at atmospheric pressure. The boiling points are “theoretical”because these materials crack or coke from thermal decomposition beforethey reach such temperatures. As such, the oil refining industryconsiders materials with boiling points <1000° F. as “volatilematerials.” In contrast, combustion science (via ASTM Test MethodD-3175) defines volatile combustible materials (VCM) as the weightpercent of the fuel that is vaporized at temperatures less than 950° C.(1742° F.). Therefore, materials that are vaporized between 1000° F. and1742° F. are considered volatile materials by combustion science, butnot by the oil refining industry, in general. Consequently, the VCM inthe petroleum coke is expected to be a combination of:

[0117] (1) unreacted coker feedstocks that vaporize between residua BPCutpoints (e.g. 1000° F.) and 1742° F.;

[0118] (2) cracked components that vaporize between drum temperature(e.g. 870° F.) and 1742° F; and

[0119] (3) cracked components that vaporize below drum temperature (e.g.870° F.) trapped in the coke.

[0120] Since steam stripping of the porous petroleum coke is typicallyconducted for 1 to 3 hours in the decoking cycle, the VCM of traditionalcoke is expected to consist mostly of (1) and (2). However, undercertain conditions, the coke VCM may have weak chemical bonds to thecoke that prevent steam stripping. The activation energies required tobreak these weak chemical bonds can be provided by the initial phases ofcombustion or ASTM Method D 3175. Note: The drum temperatures for thecracked components of (2) and (3) need to be adjusted for drum pressuresto determine comparable boiling points at equivalent conditions.Throughout this patent application, “volatile combustible materials” or“VCM” will refer to volatile combustible materials as defined by theAmerican Society for Testing and Materials (ASTM) Method D 3175. Thismethod stipulates a temperature of 950+/20° C. for seven minutes forvolatile matter content determinations.

[0121] The VCM in the coke from a delayed coker is primarily a functionof (1) feed properties, (2) drum pressure, (3) drum residence time, (4)drum temperature, and (5) the level of steam stripping in the decokingcycle. Though these parameters are noted to affect the VCM content ofthe petroleum coke, the current operating variables have no directrelationship with coke VCM. The specific impacts of these parameters arevery dependent on the feedstock composition and coker design, and varyamong refineries. Based on years of experience, general rules of thumbregarding VCM impacts have been developed and are provided below.

[0122] 1. With operating conditions held constant, a decrease infeedstock gravity typically decreases the coke VCM. The properties ofthe coker feedstocks play a major role in determining the petroleumcoke's VCM content. As noted above, the coke's volatile combustiblematerials consist of certain cracked components, as well as unreactedfeedstock components in the coke drum. Consequently, the coke VCM isdependent on the various types/qualities of the organic compounds in thefeedstock and the relative quantities of these feedstock components.

[0123] 2. With other operating conditions held constant, a reduction incoke drum pressure has been noted to decrease coke VCM for a givenfeedstock. The coke drum pressure significantly affects the coke VCM. Areduction in coke drum pressure increases the vaporization of heaviercracked liquids or unreacted feedstocks. Thus, the coke VCM iseffectively decreased by the release of these compounds that wouldotherwise remain with the coke. However, the degree of coke VCMreduction is not easy to quantify and predict for a specified level ofpressure change.

[0124] 3. Reductions in cycle time have been noted to increase the cokeVCM. The drum residence time significantly affects the VCM in thepetroleum coke. As the coking cycle time decreases, the drum fill rateincreases, and the residence time for thermal cracking and cokingmechanisms decreases. Consequently, the reactions are less complete,leaving more unreacted or partially reacted feedstock on the coke asvolatile combustible material.

[0125] 4. With other operating conditions held constant, an increase inthe drum vapor line temperature is noted to decrease the coke VCM for agiven feedstock. The drum temperature is a major factor in determiningthe VCM in the petroleum coke. The local temperatures in the drumdetermine the degrees of thermal cracking and coking of the feedstockcomponents. The temperature of the vapors leaving the drum during thecoking cycle (i.e. drum vapor line temperature) is often used as themeasured parameter to represent the average coke drum temperature. Thistemperature is typically 50-100° F. lower than the heater outlettemperature. The temperature difference is primarily due to acombination of heat losses: (1) the endothermic reactions of the thermalcracking and coking mechanisms, (2) vaporization energy of the crackedcomponents, and (3) drum heat loss. Since the asphaltic coking mechanismis a physical change with no heat of reaction, the drum vapor linetemperature (e.g. 870° F.) will likely differ significantly for variousfeedstocks. That is, different proportions of thermal coke and asphalticcoke mechanisms will impact the drum vapor line temperature differently.For a given feedstock, a higher drum vapor line temperature will causegreater cracking reactions and/or vaporize heavier cracked components,reducing the coke VCM. The drum vapor line temperature is normallycontrolled by the heater outlet temperature and the amount of condensedrecycle.

[0126] 5. The steam-stripping step of the decoking cycle is noted todecrease the coke VCM. The steam stripping during the decoking cycle hasless significant impact on the coke VCM. For example, omitting the “bigsteam” step (the initial 0.5-1 hour of the decoking cycle) will leaveslightly more wax-tailing-type material on the coke. Again, the cokeVCM, under certain conditions, may have weak chemical bonds to the cokethat prevent steam stripping.

[0127] E. Process Control of the Present Invention

[0128] The primary improvements of the present invention aremodifications to the operating conditions of the delayed coking process,in a manner that is not suggested by prior art. In fact, these changesin operating conditions are contradictory to the teachings and currenttrends in the prior art. As noted previously, the operating conditionsof the prior art give first priority to maximizing the efficiency offeedstock conversion to cracked liquid products or maximizing cokerthroughput. In contrast, the operating conditions of the presentinvention give first priority to increase and consistently maintain theconcentration of volatile combustible material (VCM) in the resultingpetroleum coke to 13-50 weight % VCM (preferably 15-30% VCM). Secondpriority is given to consistently provide a minimum-acceptable level ofsponge coke in the product coke. The third priority is THEN given tomaximize coker throughput and/or the conversion of coker feedstock blendto cracked liquid products. In many cases, the reduction of crackedliquids yield is expected to be <5% due to optimization of embodimentsof the present invention that reduce the overall VCM increase and/orminimum sponge coke, required for acceptable combustion. In some cases,implementation of the present invention can actually increase overallcracked liquids production via increased coke throughput capacity. Theoperating conditions required to achieve the objectives of the presentinvention were surprisingly modest, yet specific, relative changes fromthe prior art.

[0129] As discussed previously, delayed coker operating conditions varygreatly among refineries, due to various coker feedstocks, cokerdesigns, and other refinery operations. Therefore, specific operatingconditions (i.e. absolute values) for various refinery applications arenot completely possible for the present invention. However, specificchanges relative to existing operating conditions provide specificmethods of operational change to achieve the desired objectives.

[0130] (1) Increased VCM in Delayed Coke:

[0131] Modifications in the delayed coker operating conditions arenecessary to achieve the production of a premium, “fuel-grade” petroleumcoke. These modifications increase and consistently maintain thequantity and quality of VCM content in the petroleum coke at a specifiedlevel. This new product specification for coke VCM should be the minimumlevel that achieves a stable combustion during various operating/loadconditions for the end-user in its particular combustion system. The VCMproduct specification is expected to be in the target range of 13-50weight percent (preferably 15-30 wt. %). From the refiner's perspective,the increase in VCM should be minimized and would preferably come fromfeedstock and/or cracked components that are vaporized between 1000° F.and 1742° F. These components are less valuable to the refiner and couldconceivably include unreacted feedstock and residual compounds afterthermal cracking, as noted above. From a combustion perspective, acertain amount of the VCM increase should come from higher quality VCMcomponents that vaporize <1000° F. (preferably <850° F.) to helpinitiate combustion of the coke. In fact, each combustion system willlikely have an optimal blend of volatile components (i.e. >1000° F. vs.<1000° F.) that minimize the overall VCM specification. Thus, the idealmodifications to operational variables would achieve this optimal blendof volatile components that minimize the overall VCM increase in thepetroleum coke, and provide narrow VCM target range for quality control.

[0132] As noted above, many operational variables indirectly affect thecoke VCM. As such, the selection of the appropriate modifications in thedelayed coker operating conditions is not straightforward. In manycases, changes in the feedstock gravity and reductions in coker cycletime tend to increase the coke VCM, but provide limited change in VCMquality. Increases in drum pressure tend to increase the quality andquantity of coke VCM, but can be difficult to control coke VCM within anarrow target range. The reduced steam stripping in the decoking cyclehas been noted to have limited effect on coke VCM content. However,reduced coke drum temperatures tend to increase and maintain both thequality and quantity of coke VCM. Reduced coke drum temperatures candecrease the cracking reactions, increasing unreacted feedstock andpartially cracked components. In most cases, it provides a lowervaporization temperature in the coke drum, leaving lighter cracked orunreacted hydrocarbon components (i.e. higher quality VCM) integrated inthe coke. In addition, the coke VCM content can be more predictable viareduced drum temperatures (vs. other operational variables). As such,coke VCM content can be readily controlled within a specified range.Furthermore, reduced coke drum temperatures have the added benefit ofimproving the coke crystalline structure (See below). Consequently,reduced coke drum temperatures was selected as an exemplary means ofincreasing coke VCM to achieve the objectives of the present invention.

[0133] Based on this analysis, a simple and exemplary means ofincreasing and maintaining the volatile content of the coke (i.e. to aconsistent level between 13 and 50 wt. % VCM) would result from areduction of the average drum temperature by 5-80° F. (preferably 5-40°F.). That is, a reduction in average coke drum temperature from currentoperating conditions that produce 8-12 wt. % VCM for a given cokerdesign and feed quality. In general, an average drum vapor linetemperature of 770 to 850° F. can provide VCM levels of 15-30% for manycokers and their respective feedstocks. However, as noted earlier, cokerfeedstocks vary considerably among refineries, and can attain 15-30% VCMoutside of this temperature range. In these situations, the relativetemperature drop from the existing average drum temperature is expectedto be similar. This lower drum temperature would sufficiently reduce thecracking and coking reactions to produce the desirable increase in VCMin the petroleum coke for many existing refineries. While it is believedthis result is primarily due to (1) reductions in cracking reactions and(2) increases in unreacted coker feedstock and partially cracked liquidsremaining with the resultant petroleum coke, the present inventionshould not be bound by this.

[0134] The simplest means to achieve the lower average drum temperatureis to decrease the heater outlet temperature, accordingly. That is, theheater outlet temperature is the primary independent variable that canbe controlled to achieve lower average drum temperature. Changing theset point for the temperature controller 22 can reduce the fuel rate,and lower the heater outlet temperature to the desired level. However,as noted above, there is no direct relationship between the heateroutlet temperature, the average drum temperature, and VCM in theresulting petroleum coke. More specifically, the volatile content of thecoke significantly depends on the composition of the coker feed and therelative impacts of the competing cracking and coking reactions on itscomponents. Thus, the VCM varies significantly due to the differentcompositions in various coker feedstock blends. Consequently, theoptimal heater outlet temperature (to consistently produce the desirableVCM content in the coke) is expected to require the development ofempirical data in pilot plant studies for different coker designs andcoker feedstocks. Ideally, this new empirical data would not onlyaddress the impact of various crude oil mixtures processed in therefinery, but also evaluate the impact of other refinery operations.This type of temperature control is analogous to other coker processcontrols.

[0135] Regardless of the types of volatile components, the VCM increasewill usually create additional porosity of the residual carbon in thecombustion process. That is, the vaporization of these components in thecombustion process create greater voids and, thus, more oxidationreaction sites in the residual carbon. In addition, a VCM increase andthe associated porosity increase are also expected to further decreasethe hardness of the coke. In many cases, the softer petroleum coke canbe ground to smaller particle size distribution at the same or lessenergy in the current pulverization equipment. Consequently, bothgreater porosity and lower hardness provide better combustioncharacteristics, and reduce the overall VCM specification required toachieve acceptable combustion.

[0136] (2) Acceptable Delayed Coke Crystalline Structure:

[0137] Sponge coke is the most desirable crystalline structure forfuel-grade petroleum coke. Needle coke is too dense for good combustionproperties. Shot coke is spherical in shape, and is usually denser andharder than sponge coke. These characteristics make shot coke difficultto grind to a desired particle size distribution and more difficult toburn, particularly its carbon residue. Sponge coke, on the other hand,has a high porosity that increases with VCM. This high porosity makessponge coke much softer; easier to drill from the coke drum and easierthan other cokes (and most coals) to grind to the desired particle sizedistribution for optimal combustion characteristics. The high porosityof sponge coke (vs. most coals) also provides a greater (or comparable)density of oxidation reaction sites in the carbon residue after theinitial combustion. This combustion characteristic promotes bettercarbon burnout, which translates to shorter residence time requirements,lower burnout temperature requirements, and higher combustionefficiency.

[0138] Consequently, the second priority of the present invention'sprocess control is to consistently maintain levels of sponge coke abovea “minimum-acceptable” specification. As noted previously, the spongecoke crystalline structure has higher porosity and lower hardness(discussed below) than shot or needle coke. These qualities are moreconducive to good combustion characteristics. Ideally, the entire cokeproduct would be sponge coke crystalline structure with higher VCM (e.g.15-30 wt. %). This high-VCM sponge coke has significantly greaterporosity and lower hardness than traditional sponge coke crystallinestructure with lower VCM (e.g. 8-12% wt. %). However, with the highlevel of asphaltenes and resins in modern, heavy coker feedstocks, thisideal may be difficult to achieve. Even so, the ratio of asphaltic tothermal coking mechanisms must be reduced sufficiently to consistentlyprovide at least the minimum acceptable level of sponge coke for goodcombustion by the end-user. Since the degree of the asphaltic cokingmechanism is primarily a function of coker feedstock, an increase in thethermal coking mechanism will likely achieve the desired result.

[0139] In an exemplary embodiment, the decrease in heater outlettemperature lowers the average drum temperature to increase coke VCM(See above). This lower drum temperature favors the thermal cokingmechanism and promotes the formation of high porosity sponge coke(versus shot coke). In this manner, the lower drum temperature of anexemplary embodiment is expected to increase the degree of thermalcoking mechanism sufficiently to reduce shot coke to acceptable levels.The new product specification for “minimum-acceptable” sponge cokeshould be the minimum sponge coke required to achieve a stablecombustion during various operating/load conditions for the end-user inits particular combustion system. It should be noted that a low“acceptable” sponge coke specification may be caused by or require ahigher VCM specification. Consequently, the sponge coke and VCMspecifications can be optimized for each application relative to theparticular refinery and coke end-user (as set forth herein). The“minimum-acceptable” sponge coke product specification is expected to bein the target range of 40-100 weight percent (preferably 60-100%), forcombustion systems designed for bituminous coals.

[0140] Alternatively, a “maximum-acceptable” shot coke specification ora specification for average coke density (gm/cc) can provide otherproduct quality measures for process control of a particular cokerdesign and feedstock. A “maximum-acceptable” shot coke specification hasthe reverse logic of the above discussion. Consequently, a new productspecification for “maximum-acceptable” shot coke should be the maximumshot coke that achieves a stable combustion during variousoperating/load conditions for the end-user in its particular combustionsystem. A “maximum-acceptable” shot coke product specification isexpected to be in the target range of 0-60 weight percent (preferably5-30%), for combustion systems designed for bituminous coals. Similarly,a product specification for average coke density could be developed toprovide coke quality control. That is, the desirable high VCM spongecoke (e.g. 0.75-0.85 gm/cc) has a significantly different density thanshot coke (e.g. 0.9-1.0 gm/cc) or needle coke. Consequently, the maximumaverage coke density specification would likely reflect the compositionof the upgraded petroleum coke for the “minimum-acceptable” sponge cokeor the “maximum-acceptable” shot coke specifications.

[0141] F. Low-Level Decontamination of Coker Feedstocks; DesaltingOperations

[0142] As noted previously, the combustion of petroleum cokes containinghigh concentrations of sulfur, sodium, and some heavy metals (e.g.vanadium and nickel) has caused great apprehension due to potentialslagging and corrosion of the firebox and downstream equipment. However,the effects of petroleum coke's high metals content in combustion andheat transfer equipment is not well understood or defined. The amount ofslag formation on tubes (and associated corrosion) depends on theultimate composition of the ash resulting from competing oxidationreactions. An analysis of potential ash constituents from the combustionof these petroleum cokes (See Table 1) indicates that compounds withmelting points <2500° F. predominantly contain sodium (e.g. varioussodium sulfates and various sodium vanadates). Only four major compoundswithout sodium are in this class: vanadium pentoxide, nickel sulfate,aluminum sulfate, and ferric sulfate. However, the lower oxides of thesemetals (i.e. V, Ni, Al, and Fe) can be predominant (e.g. in a limitedoxidation environment) and have melting points in excess of 2850° F.Also, ferric sulfate and certain sodium sulfates decompose at atemperature near their melting points. Based on this analysis, theprimary element that forms compounds with detrimental firebox effects issodium. Thus, as long as the sodium content of the coke remains low, thehigh vanadium, nickel, and aluminum contents do not appear to createsignificant ash fusion and associated corrosion. Even with higher sodiumlevels in the crude, improvements in desalter operations can provide theneeded control.

[0143] Traditional desalting operations in oil refineries are primarilydesigned to remove various water-soluble impurities and suspended solidsthat are usually present in the crude oils from contamination in theground or in transportation. The prior art of desalting focuses on theremoval of salts in a manner that substantially reduces corrosion,plugging, and catalyst poisoning or fouling in downstream processingequipment. Most, if not all, oil refineries have desalting operations.One to two stages of desalting units in series are typically used topretreat the crude oils prior to the atmospheric crude oil distillationcolumns. A third desalter stage can be added for vacuum distillationresiduals and other coker feedstocks, where undesirable componentsnormally concentrate. One stage is common, two stages are typical, butfew installations use three. The additional stages can increasereliability and obtain additional reduction in the salt (and thussodium) content of the crude oil and downstream products. For example,typical salt contents of crude oil range from 260-300 g/100m³ or roughly40 pounds per thousand barrels (ptb) of crude. The first stage can bedesigned and operated to reduce the salt content by >90% to <4.0 ptb(significantly <15 ppm sodium content). Two-stage desalter operationscan be designed and operated to reduce the salt content by >99% to <0.2ptb (significantly <5ppm sodium content). Finally, a third stagedesalter can be designed and operated to reduce the sodium content oftypical vacuum residuals to <1.5 ptb (or <5 ppm sodium). This leveltypically translates to <25 ppm (or <0.05 lb./Ton) of sodium in thepetroleum coke. Consequently, current desalting technology is capable ofsufficiently reducing sodium in the petroleum coke to levels thatinhibit (and substantially reduce) sodium compounds that cause ashproblems in combustion systems. Furthermore, the additional stages alsoprovide incremental reductions in other metals (Vanadium, Nickel, etc.)and particulates that promote the precipitation of shot coke.

[0144] The present invention does not claim novel desalting technology,but provides a novel application of such technology to eliminate (orsubstantially reduce) potential ash problems associated with thecombustion of petroleum coke. Therefore, further description of readilyavailable desalting technologies was not deemed appropriate, at thistime. However, modifications to existing, desalter operations may berequired to achieve acceptable sodium levels in the petroleum coke. Thatis, the actual performance of the current desalter operation at specificrefineries depends on various design factors and operating conditions.In the past, the increased investment cost for multiple stages wasusually justified by reducing the problems in downstream processingequipment (corrosion, plugging, & catalyst poisoning or fouling); notsodium levels for petroleum coke combustion. Consequently, the installeddesalting technologies may not be currently designed and/or operated toaccomplish this objective.

[0145] An exemplary embodiment of the present invention uses threedesalting stages to pretreat the crude oil (stages 1 and 2) and cokerfeedstock components (stage 3). The 3-stage desalting system:

[0146] (1) minimizes or substantially reduces the concentration ofsodium in the resultant pet coke,

[0147] (2) promotes additional removal of other metals: Vanadium,Nickel, Aluminum, etc., and/or

[0148] (3) provides greater reduction in particulates that promote theprecipitation of shot coke.

[0149] Trace quantities of acid, caustic, and other chemical orbiological additives can be injected into any or all stages to promoteremoval of specific undesirable compounds. For example, trace quantitiesof acid can be added to the water wash in the first stage to promoteadditional removal of sodium, other alkali and alkaline earth metals,and heavy metal compounds in the crude oil. Trace quantities of causticcan be added to the water wash in the second stage to promote additionalremoval of sulfur compounds in the crude oil. However, sodium compounds,such as sodium hydroxide, should not be used, and reintroduce higherlevels of sodium. Trace quantities of other chemical additives can beadded to the water wash in the third stage to promote removal of othercompounds of concern. However, since our primary goal is the removal ofsodium and other metals, trace quantities of acid in all three stagescan be desirable to maximize their reduction.

[0150] G. Impacts of the Present Invention on Refinery Operations

[0151] The above embodiment of the present invention may causeadditional positive impacts on various refinery operations. First ofall, the reduced drum temperature (and associated decrease in heateroutlet temperature) can normally improve the delayed coker's operation &maintenance and the quality of its cracked liquid products. Secondly,any reduction of shot coke crystalline structure can substantiallyreduce coker operational problems, as well as improving combustioncharacteristics. Thirdly, the 3-stage desalting operation improves theoperation and maintenance of the coker and other refinery operations.Finally, all of these operational changes can also provide greaterflexibility in debottlenecking options for increasing the coker and/orrefinery throughput capacities. Most of these advantages lead to highercoker throughput and/or lower operating and maintenance costs inlong-term.

[0152] The reduced average drum temperature of the exemplary embodimentnot only increases the coke VCM to the desired level, but also providesother advantages in the coker operation. First, the lower drumtemperature favors thermal coke formation and promotes higher porositysponge coke. This upgraded petroleum coke is substantially softer thanthe traditional petroleum coke due to its higher VCM, higher porosity,and acceptable levels of shot coke. Therefore, drilling of this softerpetroleum coke in the decoking cycle is less cumbersome, reducingdecoking time and associated maintenance. Secondly, a lower drum vaporline temperature also reduces vapor limits without increasing drumpressure and operating costs. In addition, the lower vapor velocitiesfrom the coke drums normally decrease the entrainment of coke fines tothe fractionator in the coking cycle. Thirdly, lowering the heateroutlet temperature to achieve the lower drum temperature can increasethe drum fill rate, reducing drum limits and coking cycle time. Finally,the reduced outlet temperature of the coker heater reduces the severityof the delayed coker operation, and consequently improves the cokeroperation and maintenance. This coker operational change decreases theenergy consumption and cost for each barrel processed. The lower outlettemperature also reduces the potential for coking in the heater,onstream spalling, and its subsequent failure. Reducing these factorsusually increases heater run life, which is a primary factor in cokerrun life. Also, the lower target outlet temperature typically increasescoker heater throughput capacity for a given heater and feedstock. Assuch, the reduced outlet temperature provides a greater opportunity foran increased drum fill rate, reducing drum limits and coking cycle time.Reduction in both coking and decoking cycles can lead to increased cokerthroughput.

[0153] The reduced heater outlet temperature is also expected to improvethe quality of the cracked liquid products. The subsequent thermalcracking is less severe and creates less olefinic components in the gasoils. The olefinic components tend to be unstable and form gum orsediments. As such, they are undesirable in downstream processing (e.g.catalytic cracking). In addition, the less severe cracking normallydecreases the end point and carbon residue of the heavy coker gas oil.The heavy residuum in the coker heavy gas oil can create problems indownstream processing equipment. For example, the heavy residuum in thefeed of fluid catalytic cracking units (FCCUs) often turns into coke oncatalyst, which can occupy the reaction sites of the catalyst,decreasing catalyst activity and process conversion (or efficiency). Inaddition, increasing the coke on catalyst normally increases theseverity of catalyst regeneration. In turn, severe catalyst regenerationtypically increases catalyst attrition, particulate emissions, andcatalyst make-up requirements. Consequently, an exemplary embodiment ofthe present invention can avoid these problems, improving downstreamoperations and product quality.

[0154] Improved coke crystalline structure often reduces operation andmaintenance in delayed coker. Besides improving coke grindability andcombustion, reducing the production of shot coke to acceptable levelsimproves coker operation and reduces safety hazards. Shot cokecontributes significantly to the following problems: (1) Plugging thebottom coke nozzle; inhibiting proper cooling steam, quench water, anddrainage; increasing coking cycle, (2) Channeling of quench water;creating coke drum hot zones and dangerous conditions during cutting,and (3) Coke pouring out of the drum; endangering cutting crew.Consequently, reductions in the shot coke alleviate these operationalproblems. In addition, the softer sponge coke with the higher VCM isless likely to produce coke fines from the decoking operation. In turn,less coke fines reduces erosion of the coke cutting nozzles.

[0155] The 3-stage desalting operation can improve the operation andmaintenance of the delayed coker and other refinery operations. Sodiumlevels >15-30 ppm in the coker feedstocks are known to accelerate heatercoking. The efficient desalting normally (1) inhibits coking in theheater, (2) decreases the need for onstream spalling, and (3) increasescoker heater run life. Efficient removal of certain particulates alsoinhibits the formation of shot coke. Most importantly, high efficiencydesalting substantially decreases corrosion in atmospheric and vacuumcrude distillation units and other downstream operations.

[0156] Finally, all of these operational changes can also providegreater flexibility in coker and refinery deboftlenecking options. Ascoker feedstocks change over time, coker throughput (and often refinerythroughput) is limited by the particular coker design. Major designlimitations are alleviated:

[0157] (1) Heater (or Temperature) Limited: Reduced heater outlettemperature (as noted above) provides the opportunity to safely increaseheater capacity with reduced heater coking and online spalling, whileincreasing heater (and potentially coker) run life(s)

[0158] (2) Fractionator (or Vapors) Limited: Reduced severity in thermalcracking will reduce the cracked vapors per barrel going to thefractionator; potentially increasing coker capacity

[0159] (3) Coke Drum (or Coke Make) Limited: Increased drum fill rateand decreased cutting time can be used to reduce coking and decokingcycles to increase coker throughput

[0160] (4) Sour Crude Processing: High efficiency desalting reducescorrosion in various refinery processes and increases the refinery'stolerance of higher crude sulfur levels

[0161] (5) Heavy Crude Processing: Decreased cycle time can increasecoker throughput capacity, even with increased coke yield (e.g. 2 hr˜10-15%) and allow heavier crude residua content

[0162] Since the coker is often the bottleneck in the crude throughputof many refineries, debottlenecking the coker can also translate intoincreased refinery throughput. In addition, factors (4) and (5) providegreater flexibility in crude blends and the ability to processinexpensive heavy, sour crudes. Thus, the overall changes in cokeroperation are expected to include optimization of various cokingparameters, crude blends, and other refinery operations, andmaximization of coker and refinery throughputs.

[0163] 2. Use of Premium “Fuel-Grade” Petroleum Coke: ConventionalUtility Boilers

[0164] An exemplary use of this new formulation of petroleum coke is thereplacement of most types of coals in conventional, pulverized-coal (PC)boilers, utility, industrial, and otherwise. As noted above, theupgraded petroleum coke of the present invention has fuelcharacteristics that are superior to many coals, which are currentlyused in conventional PC utility boilers. The discussion of thisexemplary embodiment includes (a) a basic description of a conventionalPC utility boiler system with. traditional particulate control devices,(b) the combustion process of the prior art, (c) the combustion processof the present invention and its improvements, (d) the environmentalcontrols of the prior art, and (e) the environmental controls of thepresent invention and their impacts. Finally, an example is provided, atthe end of this discussion, to illustrate the principles and advantagesof the exemplary embodiments of the present invention.

[0165] When appropriate, comparisons are made to typical bituminouscoals, only for the sake of examples. Similar comparisons exist forother coals, as well. The most important improvements in the use of theupgraded petroleum coke are the abilities to maintain stable combustionwithout auxiliary fuels and substantially reduce environmentalemissions. In particular, only modest modifications are required tosubstantially reduce emissions of sulfur oxides, while burning a fuelwith significantly higher (or comparable) sulfur content in the fuel.

[0166] A. Conventional, Pulverized-Coal (PC) Utility Boiler; ProcessDescription

[0167] As defined here, conventional, pulverized-coal utility boilersinclude (but are not limited to) various coal combustion systems used bypower utilities to produce steam and subsequently electricity via steamturbines. Typically, the coal combustion system employshorizontally-fired coal burners that produce intense flames in a highheat capacity furnace. A high heat capacity furnace has tremendouscapacity to absorb the intense heat released by the combustion of thecoal. The most common type of high heat capacity furnace is lined withtubes filled with water, often called a water-wall furnace. Thehorizontally-fired burners are normally suspension burners, which conveyfine, pulverized coal particles via air (i.e. suspended by air) to thecombustion zone. Pulverized coal (PC) is usually provided to the burnersby a single, fuel processing/management system, which pulverizes,classifies, and regulates the flow of the coal. Pulverization to thedesirable particle size distribution of coal particles is key toachieving good combustion characteristics. Also, the coal combustionsystem normally includes additional flue gas heat exchange, sootblowingequipment, and various temperature controls to optimize efficient use ofenergy.

[0168] In an exemplary embodiment of the present invention, aconventional, pulverized-coal utility boiler with a traditionalparticulate control device is modified to convert sulfur oxides to dryparticulates upstream of the existing particulate control device(s). Theprior art has been modified to achieve this objective with Option 1: aretrofit addition of flue gas conversion reaction chamber(s) and reagentinjection system(s) and/or Option 2: dry reagent injection system(s) inthe combustion system. FIG. 2 shows a basic process flow diagram forthis modified system burning a pulverized solid fuel as the primaryfuel. Auxiliary fuel, such as natural gas or oil, is used for start-up,low-load, and upset operating conditions. The solid fuel 100 isintroduced into the fuel processing system 102, where it is pulverizedand classified to obtain the desired particle size distribution. Aportion of combustion air (primary air) 104 is used to suspend andconvey the solid-fuel particles to horizontally-fired burners 108. Mostof the combustion air (secondary air) 110 passes through an airpreheater 112, where heat is transferred from the flue gas to the air.The heated combustion air (up to 600 OF) is distributed to the burnersvia an air plenum 114. The combustion air is mixed with the solid fuelin a turbulent zone with sufficient temperature and residence time toinitiate and complete combustion in intense flames. The intense flamestransfer heat to water-filled tubes in the high heat capacity furnace116 primarily via radiant heat transfer. The resulting flue gas passesthrough the convection section 118 of the boiler, where heat is alsotransferred to water-filled tubes primarily via convective heattransfer. At the entrance to the convection section 118, certain dryreagents can be mixed with the flue gas to convert undesirable flue gascomponents (e.g. sulfur oxides) to dry particulates (i.e. exemplaryembodiment: option 2). The sorbents 120 pass through a reagentpreparation system 122 and are introduced into the flue gas via areagent injection system 124. Steam or air 126 is normally injectedthrough sootblowing equipment 128 to keep convection tubes clean of ashdeposits from the fuel and formed in the combustion process. The fluegas then passes through the air preheater 112, supplying heat to thecombustion air.

[0169] The cooled flue gas then proceeds to the air pollution controlsection of the utility boiler system. At the exit of the air preheater,certain dry reagents can be mixed with the flue gas to convertundesirable flue gas components (e.g. sulfur oxides) to dry particulates(exemplary embodiment: option 2). The reagents 130 pass through areagent preparation system 132 and are introduced into the flue gas viaa reagent injection system 134. The existing particulate control device136 (ESP, baghouse, etc.) has been retrofitted with the addition of areaction chamber 138 (the exemplary embodiment: option 1). Certainreagents (e.g. lime slurry) can be prepared in a reagent preparationsystem 140. The reagent is dispersed into the flue gas through a specialinjection system 142. Sufficient mixing and residence time are providedin the reaction chamber to convert most of the undesirable flue gascomponents (e.g. sulfur oxides) to collectible particulates. Theseparticulates are then collected in the existing particulate controldevice 136. A bypass damper 144 is installed in the original flue gasduct to bypass (100% open) the retrofit, flue gas conversion system,when necessary. The clean flue gas then exits the stack 148.

[0170] B. Combustion Process of the Prior Art

[0171] The conventional, PC-fired utility boiler system, describedabove, can successfully burn a wide variety of solid fuels. Varioustypes of coal are burned in such systems throughout the United Statesand internationally. Bituminous, sub-bituminous, and lignite coals arecommonly used in this type of combustion system. Low volatile, solidfuels (such as traditional petroleum coke, anthracite coals, andlow-volatile bituminous coals) typically cannot be used as the primaryfuel in these types of boilers. These solid fuels often requirenon-conventional types of combustion systems, including cyclonefurnaces, fluidized bed combustors, or down-fired burners into a lowheat capacity furnace (e.g. refractory lined). The design of eachconventional, PC-fired combustion system, though, varies greatly anddepends on (1) each coal's respective fuel properties and combustioncharacteristics, and (2) the quantity and quality of steam required.

[0172] The integrated design of a conventional, PC-fired utility boilerand associated systems is a complex engineering effort. Various designand operational factors must be given proper consideration. These designand operational factors include (but are not limited to) the following:

[0173] Fuel Properties: VCM, ash content, moisture content, charquality, particle size distribution (PSD), carbon/hydrogen ratio, oxygencontent, adiabatic flame temperature, burning profiles, etc.

[0174] Combustion Characteristics: flame stability, flame temperature,flame turbulence, flame residence time, excess air, air preheat (primary& secondary air), carbon burnout, combustion efficiency, etc.

[0175] Burner Design: size, number, flame shape, fuel/air mixing,pressure drop, low emissions, etc.

[0176] Furnace Design: size, shape, refractory & heat transferproperties, tube layout & metallurgy, etc.

[0177] Steam System Design: water & steam quality, tube number &spacings, sootblowing, etc.

[0178] Fuel Preparation System: pulverizer capacity & energy/grindingcharacteristics, in/out PSDs, etc.

[0179] Engineers skilled in the art typically use complex computermodels to optimize the integrated design, based on substantialcombustion experience and various design factors (including those notedabove). Therefore, the remaining discussion about the combustion priorart will be limited to fuel property considerations that significantlyaffect the fuel decisions for new boilers and fuel switching in existingboilers. Though this discussion is primarily focused on various coals tosimplify explanation, the principles involved apply to other solid fuelsas well.

[0180] Numerous references discuss the combustion science related toburning solid fuels. Many provide theories of combustion and therelative impacts of various fuel properties, including ash content,moisture content, char quality, and particle size. These issues arediscussed in the present invention, where it is relevant. However, twoother fuel properties, that are not universally discussed, are key toaccurately describe the present invention. Both fuel properties,grindability indexes and burning profiles, are important factors in theevaluation of potential fuel substitutions in conventional, PC-firedcombustion systems.

[0181] (1) Grindability Index:

[0182] A fine particle size distribution of coal from the pulverizer isa critical parameter in achieving good combustion efficiency. That is,for a given coal, smaller coal particles normally require less residencetime and/or lower temperatures to provide good char burnout and lessunburned carbon. The ability to pulverize the coal to finer particlesize distributions is related to the coal's hardness. However, agrindability index provides a more comprehensive comparison of theoverall grindability of various coals.

[0183] Babcock & Wilcox developed one type of grindability index test,called the Hardgrove Grindability Index (HGI). This laboratoryprocedure, ASTM Method D 409, is an empirical measure of the relativeease with which coal can be pulverized. The HGI has been used for thepast 30 years to evaluate the grindability of coals. The method involvesgrinding 50 grams of air-dried test coal (16×30 mesh or 1.18 mm×600 um)in a small ball-and-race mill. The mill is operated for 60 revolutionsand the quantity of material that passes through a 200 mesh (75 micron)screen is measured. From a calibration curve relating -200 mesh (-75micron) material to the grindability of standard samples supplied by theU.S. Department of Energy, the Hardgrove Grindability Index (HGI) isdetermined for the test coal. The higher the HGI, the more easily thecoal can be pulverized to fine particle size distributions. Pulverizermanufacturers have developed correlations relating HGI to pulverizercapacity at desired levels of fineness.

[0184] (2) Burning Profiles:

[0185] As noted above, many fuel properties need proper consideration inthe integrated design of a solid-fuel combustion system. One of the mostcomprehensive evaluations of the overall combustibility of a solid fuelis the burning profile. One type of burning profile test was developedby Babcock & Wilcox. This laboratory procedure measures the entirecourse of combustion for a tested fuel, from ignition to completion ofburning.

[0186] The B&W procedure, described by Wagoner and Duzy, uses derivativethermogravimetry, in which a fuel is oxidized under controlledconditions. A 300 mg sample with a particle size less than 60 mesh (250microns) is heated at a fixed rate (27° F. per minute: 68 to 2012° F.)in a stream of air. Weight change (mg/min) is measured continuously. Thegraphical presentation of these data (mg/min vs. temperature) provides amore complete picture of the entire combustion process, throughexamination of the solid fuel's oxidation rates. For example, FIG. 3shows the burning profiles representing each classification of coal. Theheight of each oxidation peak is proportional to the intensity of theoxidation reactions and flame. The area under each peak is noted to beapproximately proportional to the amount of combustible material in thesample and/or the total heat liberated. In general, bituminous,sub-bituminous, and lignite coals have greater oxidation rates at lowertemperatures than anthracite coals. This indicates easier ignition andburning. Such fuels would be expected to burn more completely in thelower part of the furnace. Profiles that extend into very hightemperature ranges, such as anthracite coal, indicate slow burning fuelsfor which longer residence times in high temperature zones are necessaryfor efficient combustion. Thus, the maximum temperature on the burningprofile helps determine the requirement for furnace residence time athigh temperature to obtain a low unburned carbon loss, and thus highercombustion efficiency.

[0187] Burning profiles are very repeatable for the same operatingconditions and test furnace. However, the same solid fuel will show adifferent burning profile for changes in heat transfer rates, samplesize, particle size distribution, air flow rate, etc. Consequently, theburning profiles provide a good qualitative comparison of relativeburning properties for solid fuels, but can be limited to combustionwith identical or very similar conditions.

[0188] A major shortcoming of the B&W burning profile test procedure isthe preparation of the various fuel samples at a specified particle sizedistribution. The fuel sample is ground to less than No. 60 Sieve (˜250microns) and care is specified to produce a minimum of fines. Incontrast, various coals are pulverized to 60-90% through 200 Sieve (˜74microns) for various combustion applications. As discussed previously,the particle size distribution has a substantial impact on a solidfuel's oxidation rate. Consequently, a modified test procedure isdesirable to reflect relative differences in HGI and the grindabilitycharacteristics for various fuels. For example, the burning profile testprocedure can be modified to prepare fuel samples with a constantgrinding energy, yet minimize the generation of fines. For testingpurposes, the fuel samples would still have a particle size distributionthat is much larger than the commercial facility. In this manner, therelative combustion impacts of fuel grindability and resultant particlesize distribution can be incorporated into the burning profile.

[0189] (3) Fuel Substitution:

[0190] Burning profiles can be effectively used to evaluate thepotential substitution of one solid fuel for another. Coals with similarburning profiles have been noted to behave similarly in large furnacesof equivalent design and operation. Thus, comparison of the burningprofile of an unknown solid fuel to that of a solid fuel that has provenperformance can provide useful information to predict design (e.g.furnace & burners) and operating conditions (e.g. excess air and burnersettings). Furthermore, comparison of the burning profiles for analternative solid fuel and a solid fuel with proven performance in aparticular furnace design can provide a preliminary evaluation of theability to substitute one fuel for another in a particular combustionsystem.

[0191] Similar burning profiles provide a higher degree of confidence inthe ability to substitute one solid fuel for another. However, a perfectmatch of burning profiles is not necessary, and can be undesirable. Forexample, the first peak in the burning profile of coals with highmoisture is the evaporation of the coal's water content. Providing asubstitute solid fuel with this burning profile characteristic can beundesirable due to the detrimental combustion effects of moisture. Also,very volatile fuels may be undesirable due to concerns of prematureignition and excessive flame intensity. Furthermore, a low temperaturepeak from low-quality volatiles (e.g. carbon monoxide) can be lessdesirable due to its effects that cause lower heating value and higherfuel usage. Consequently, the comparison of burning profiles is apreliminary evaluation, which requires further optimization of basicfuel properties and combustion characteristics.

[0192] Optimal ignition and char burnout are key properties in achievinga successful solid fuel switch. Optimal ignition characteristics wouldprovide self-combustion in a conventional PC boiler without auxiliaryfuel, while avoiding premature ignition, excessive flame intensity, orlower heating value. Optimal char burnout would provide high combustionefficiencies (i.e. insignificant unburned carbon) at sufficiently lowtemperatures and residence times to complete combustion in the lowerfurnace, while avoiding excessive flame intensity.

[0193] Finally, derating the boiler's capacity and reducing efficiencyare major concerns of fuel switching. As such, switching an existingsolid fuel to a higher quality fuel is often preferable to switching toa lower quality fuel. For example, most of the western U.S. low sulfurcoals are sub-bituminous rank that have higher moisture, comparable ash,and lower quality volatiles than bituminous coals being replaced.Consequently, their lower heating values (and capacity derating effect)limit their application to partial substitution or boilers with low loadfactors. However, in certain situations, the reduction in sulfur oxidesemissions is more important than the ability to maintain high loadfactors.

[0194] C. Combustion Process of the Present Invention

[0195] The new formulation of petroleum coke of the present inventionhas an unexpected ability to burn successfully, even with relatively lowVCM content. The combustion of this upgraded coke is compared totraditional delayed coke and most coals. Its superior fuel propertiesand combustion characteristics are discussed, including ash/moistureeffects, char quality (particle size, porosity, etc.),ignition/residence time issues, and burning profiles. Finally, superiorcharacteristics of the upgraded petroleum coke are then discussed foreach of the following subsystems of the conventional PC utility boiler:fuel processing, combustion, and heat transfer.

[0196] (1) Combustion Quality of Traditional Petroleum Coke:

[0197] A burning profile representing a traditional petroleum coke wasadded to FIG. 3 for comparison to burning profiles of various types ofcoal. In general, this traditional petroleum coke has a burner profilesimilar to low-volatile, bituminous coal. Other traditional petroleumcokes (e.g. shot and Fluid coke) have burner profiles more similar toanthracite coals. In either case, the similar burner profiles show whytraditional petroleum cokes require low heat capacity furnaces commonlyused for these coals (e.g. cyclone furnaces). As such, traditionalpetroleum coke can only be considered for direct fuel substitution inspecial furnaces capable of firing these hard-to-burn coals.

[0198] Further analysis of this traditional petroleum coke's burningprofile demonstrates even poorer combustion characteristics than these“similar” coals. First, the initial ignition temperature (˜600-650° F.)is comparable to low-volatile bituminous and high-volatile anthracitecoals, but significantly higher than high volatile bituminous,subbituminous, and lignite coals. This higher initial temperature ofweight loss in the burning profile is caused by the low-quality,volatile content of the traditional petroleum coke. Secondly, themaximum rate of weight loss (oxidation peak) for this traditionalpetroleum coke is ˜10-20% lower than most coals. This lower oxidationpeak can be attributed to the coke's lower quality/quantity of VCM (11.7wt. % VCM) and poor char quality (e.g. shot coke). That is, the coke'sdevolatilization and char burnout are not as rapid, creating loweroxidation intensity. Thirdly, the area under the curve is significantlysmaller than the coal's, indicating the total sample did not oxidize.With complete combustion, the traditional petroleum coke would beexpected to have a larger area under the curve, representing relativelygreater proportion of combustible material due to its much higherheating value and lower ash/moisture contents. This unburned carbon canbe caused by several factors, including the coke's lowerquality/quantity of VCM and poor char quality. Finally, the completionof combustion occurs at approximately 1550-1600° F. This undesirable,combustion completion temperature is again comparable to low-volatilebituminous and high-volatile anthracite. Profiles that extend into thesehigh temperature ranges indicate slow-burning fuels, which requirelonger residence times in high temperature zones for efficientcombustion.

[0199] In conclusion, this burning profile analysis indicates theproduction of a petroleum coke that sustains self-combustion may requiremore than simply an increase in coke VCM. Substantial coke combustionexperience of the inventor further supports this conclusion. Variouscoke/oil slurries that simply add VCM external to the coking processhave been attempted with limited success. The oil provides a highquantity of high-quality VCM. However, this method does not change thepoor char quality. Similarly, a higher quantity of low quality VCM isnormally not sufficient to initiate and sustain self-combustion withouta substantial change in the coke's char quality.

[0200] (2) Combustion of Upgraded Versus Traditional Petroleum Coke:

[0201] The new formulation of petroleum coke in the present inventionhas substantially better fuel properties and combustion characteristicsthan the traditional “fuel-grade” petroleum coke. The primary differenceis the ability to initiate and sustain self-combustion in aconventional, high heat capacity furnace without the use of auxiliaryfuels, except for start-up. For example, the upgraded coke, unliketraditional coke, can be effectively burned in a conventional,pulverized-coal boiler. The superior combustion characteristics resultfrom 3 primary changes in the new formulation of the exemplaryembodiment:

[0202] (1) Increased quantity and quality of VCM: improves ignition andchar burnout,

[0203] (2) Improved char quality of the modified sponge coke: higherporosity and reactivity, and

[0204] (3) Softer coke: ability to pulverize to a smaller particle sizewith same or less energy input.

[0205] The combined effect is expected to have the following impact onthe petroleum coke's burning profile: (1) move the burning profile curveto the left (i.e. lower ignition and combustion completiontemperatures), (2) increase maximum rate of weight loss (or peak flameintensity), and (3) increase the area under the curve (increaseproportion of combustible material oxidized). These factors improve theignition, char burnout characteristics, flame quality, and combustionefficiency.

[0206] Further embodiments of this invention provide additional means toincrease the quality and quantity of the volatile combustible materialsin the upgraded petroleum coke. These other embodiments provide optionsto improve further the combustion characteristics of the upgradedpetroleum coke. With these additional embodiments, the upgradedpetroleum coke is expected to initiate and complete combustion at lowertemperatures and require lower combustion residence times. Consequently,the burning profiles of the upgraded coke are expected to move furtherto the left.

[0207] (3) Combustion of Upgraded Petroleum Coke Versus Most Coals:

[0208] The fuel properties and combustion characteristics of petroleumcoke are improved sufficiently by the present invention to replace mostcoal fuels (e.g. in conventional, PC utility boilers). An exemplaryembodiment of the present invention is expected to improve petroleumcoke sufficiently to directly replace many high volatile bituminous,subbituminous, and lignite coals. In cases where direct replacement isnot possible, the improved qualities are sufficient to replace thesecoals with modest to moderate modifications in the design and/oroperation of the combustion system (i.e. burners, furnace, etc.).

[0209] a. Superior Fuel Properties:

[0210] The premium, “fuel-grade” petroleum coke typically has bettercombustion characteristics than most coals due to more desirable fuelproperties The primary coke fuel properties affecting combustioncharacteristics include the following: lower ash, lower moisturecontent, lower grindability hardness, greater fuel consistency, andsignificantly higher (or comparable) porosity of the residual carbon.Tables 2-A and 2-B provide comparison of key differences in fuelproperties, combustion characteristics, and environmental performancefor traditional petroleum cokes, upgraded petroleum cokes of the presentinvention (i.e. OptiFuel ) and many examples of various types of coal.Compared to most coals, the upgraded petroleum coke typically has 90+%lower ash content, 75-90+% lower moisture content, and 10-250+% higherheating values. The fuel rate is typically decreased by 10-40+%. Thesignificantly lower fuel rate can decrease the total quantity ofundesirable components (e.g. sulfur), even with higher componentcontents (wt. % in pet coke vs. coal). Sulfur, nitrogen, and carboncontents of the upgraded coke are normally comparable or higher. The VCMcontent is typically lower for comparable combustion characteristics(e.g. burning profile) and fuel use applications.

[0211] b. Improved Combustion Characteristics:

[0212] The superior fuel properties of the upgraded petroleum coke fromthe present invention provide improved (or comparable) combustioncharacteristics relative to most coals. More desirable combustioncharacteristics are expected to include (but are not limited to) (1)superior ash and moisture combustion effects, (2) increased residencetime, (3) better (or comparable) char quality & burnout, and (4)improved combustion stability with lower excess air rates.

[0213] 1. Superior Ash and Moisture Combustion Effects: The lower ashand moisture contents of the upgraded petroleum coke affect a variety ofcombustion characteristics. Ash and moisture absorb heat in thecombustion process. This increases the required ignition temperature andreduces the flame temperature (adiabatic and actual). Also, high ash andmoisture contents substantially reduce the heat content (Btu/pound) ofthe fuel and require more pounds of fuel for a given heat release ratein the combustion system. Consequently, lower ash and moisture contentsof the upgraded petroleum coke increases flame temperature and heatingvalue and reduces required ignition temperature and fuel rates.

[0214] 2. Increased Residence Time: The lower fuel rates and associatedreduction in air rates normally increase operating capacities in anexisting boiler for the pulverizer, fan, and boiler systems. Inaddition, the lower fuel and air rates can significantly increase theresidence time in the existing boiler system, usually improvingcombustion efficiency (e.g. carbon-burnout), boiler efficiency (e.g.better heat transfer), and environmental control efficiency (e.g.reduced ESP velocity: Q/A). In most cases, upgraded coke also decreasesflue gas flow, system pressure-drop, and associated auxiliary power.

[0215] 3. Better Char Quality and Burnout: The high porosity, spongecoke of the present invention provides better char quality that favorssuperior carbon burnout to most coals. The higher porosity provides moreaccessible combustion reaction sites, and promotes more complete carbonburnout. As discussed below, the significantly lower hardness(HGI=80-120+) allows more flexibility in grinding the coke to a muchfiner particle size distribution at lower grinding energies. The finerparticle size of the fuel promotes more efficient and completecombustion, particularly for a low VCM fuel.

[0216] 4. Improved Combustion Stability with Lower Excess Air: Theupgraded petroleum coke is produced by a chemical process that providesless variability in composition and combustion characteristics thancoal(s) from different veins in the same mine or even different mines.

[0217] That is, the upgraded petroleum coke of the present invention hasmore uniform fuel properties and combustion characteristics. This fuelconsistency normally improves flame stability and decreases excess airrequirements for similar load variations.

[0218] 5. Catalytic Oxidation Effects: The metals content of petroleumcoke (upgraded or traditional) often contains higher levels of heavymetals, such as vanadium and nickel. These metals can provide a positivebenefit as an oxidation catalyst to improve combustion characteristicsand efficiency.

[0219] All these factors give the upgraded petroleum coke firingcapabilities and combustion characteristics that are superior (orcomparable) to coals with significantly higher VCM content. High qualityVCM, high porosity sponge coke, and finer particle size distribution ofthe upgraded coke fuel are primary features of the present inventionthat reduce the overall VCM requirement relative to various coals. Lowash and moisture content are also contributing factors. In conclusion,the fuel qualities of the upgraded petroleum coke are expected topromote (1) a more uniform and stable flame, (2) acceptable combustionat lower excess air operation, and (3) better char burn-outcharacteristics than most coals, over a wide range of operatingconditions.

[0220] As noted above, additional embodiments of this invention provideadditional options to increase the quality and quantity of the volatilecombustible materials in the upgraded petroleum coke. That is, highquality VCM (e.g. BP Range: 350-750° F. & heating value:16-20,000+btu/lb) can be integrated into the petroleum coke crystallinestructure. In this manner, the burning profile of the upgraded coke canbe adjusted to optimize desirable combustion characteristics forreplacing solid fuels in a particular combustion system (See: OptimalFuel Embodiment). This can be accomplished by matching the burningprofile of the existing solid fuel or achieving other desirable burningprofile characteristics. For example, production of an upgradedpetroleum coke with optimal ignition and char burnout characteristicscan also be achieved. Again, in cases where direct replacement is notpossible, the improved qualities are sufficient to replace these coalswith modest to moderate modifications in the design and/or operation ofthe combustion system (i.e. burners, furnace, etc.).

[0221] (4) Combustion of Upgraded Petroleum Coke vs. Low Sulfur Coals:

[0222] Most low-sulfur coals referred to in this section are actually asubset of the previous section (i.e. most coals). Consequently, thecomparison of fuel properties and combustion characteristics are stillvalid in this section. However, low-sulfur subbituminous coals are aspecial subset of “Most Coals” that warrants further discussion, due totheir current use as fuel alternatives to comply with U.S. environmentallaws.

[0223] Many PC utility boilers in the United States are being switchedfrom bituminous coal to subbituminous, low-sulfur coal to comply withEPA regulations caused by the CAAA of 1990. The subbituminous, lowsulfur coal typically has comparable ash contents, higher moisturecontents and lower heating values (vs. bituminous coal). The fuel rateis typically increased by 20-40+%. The substantially higher fuel rateusually increases the ash quantity, even with lower ash content (wt. %).Consequently, a fuel switch to this low-sulfur coal normally requiresboiler derating (operating with lower capacity), pulverizer derating,and mitigating problems with particulate emissions. Other problems ofteninclude increases in air requirements, flue gas flow, systempressure-drop, and associated auxiliary power. Most of these factorslead to decreased combustion, boiler, and environmental controlefficiencies.

[0224] In contrast, a fuel switch to the upgraded petroleum coke of thepresent invention will have the opposite impact on most of thesefactors. Table 2-A shows that the upgraded petroleum coke (vs.bituminous coal) typically has 95+% lower ash content, 5-30+% lowermoisture content, and 10-25%% higher heating values. The fuel rate istypically decreased by 10-20+%. The significantly lower fuel rateusually decreases the overall sulfur quantity, even with higher sulfurcontent (wt. %). Consequently, a fuel switch to the upgraded cokeincreases operating capacities for the pulverizer, fans, boiler, andenvironmental control systems. Decreases in air requirements, flue gasflow, system pressure-drop, and associated auxiliary power can oftenlead to increased combustion, boiler, and environmental controlefficiencies, as well. In conclusion, fuel switching from most coals(including low sulfur, subbituminous coals) to the upgraded petroleumcoke of the present invention can significantly improve the varioussubsystems of the conventional, PC utility boiler: fuel processing,combustion and heat transfer.

[0225] (5) Fuel Processing Improvements:

[0226] The higher VCM, lower ash content, and lower hardness of theupgraded petroleum coke greatly reduce the fuels handling challenges andequipment wear. First, the upgraded petroleum coke has the capability ofbeing the only fuel required, allowing the use of one fuel processingand management system, existing or otherwise. In contrast, the prior artfor combustion of traditional, fuel-grade petroleum coke in a utilityboiler requires a coke/coal blend, which often required separate fuelprocessing systems for the coal and petroleum coke, respectively.Secondly, the upgraded petroleum coke has dramatically lower ash content(0.1-1.0 wt. %) and moisture content (.5-4.0 wt. %) than most coals(Ash=5-70 wt. % & Moisture=5 to >50 wt. %). The lower ash and moisturecontents give the upgraded petroleum coke a substantially higher heatingvalue: (13.0-15.5 MBtu/lb) than most coals (10.5-13.0 MBtu/lb).Consequently, the conventional utility boiler requires substantiallyless tons of the upgraded petroleum coke for a given heat release rate.Thirdly, the upgraded coke of this invention also is dramatically softerthan most bituminous coals, as indicated by its lower HGI of 80-120+,compared to 20-80+of typical bituminous coals and <60 for traditionalpetroleum cokes. Consequently, the existing pulverization equipment cannormally grind the upgraded coke to a much finer particle sizedistribution, at the same level of grinding energy. For example, 60-80%through 200 mesh is typical for various ranks of coals (lignite toanthracite). The upgraded petroleum coke can usually achieve 85-95+%through 200 mesh with less (or comparable) grinding energy. This veryfine particle size distribution further improves its combustioncharacteristics. Alternatively, the upgraded coke could be ground to thesame particle size distribution (or any point in between) with a lowergrinding energy and cost. Both the reduced fuel rate (e.g. Tons/hour)and the lower hardness (softer material) are expected to substantiallyreduce erosion, equipment wear, and operating & maintenance costs in thefuel processing and combustion systems.

[0227] (6) Combustion Improvements:

[0228] As discussed previously, the upgraded petroleum coke providessuperior fuel properties and improved combustion characteristicsrelative to traditional petroleum coke and most coals. The fuelproperties of the upgraded coke are superior to traditional coke due to(1) increased quantity and quality of VCM (improves ignition and charburnout), (2) improved char quality of the modified sponge coke (higherporosity and reactivity), and (3) softer coke (ability to pulverize to asmaller particle size). The fuel properties of the upgraded coke alsoprovide improved combustion characteristics relative to most coals: (1)superior ash and moisture combustion effects, (2) increased residencetime, (3) better char quality and burnout, (4) improved combustionstability with lower excess air, and (5) catalytic oxidation effects.

[0229] (7) Heat Exchange Improvements:

[0230] In most cases, the premium, fuel-grade petroleum coke is expectedto have better heat transfer characteristics and overall thermalefficiency. In operating conditions with more uniform and stable flames,the upgraded petroleum coke is expected to provide better radiant heattransfer characteristics. The much lower ash also dramatically reducesthe fouling of heat transfer surfaces and the need for sootblowing ofconvective heat exchange surfaces. The better heat transfercharacteristics, reduced fouling, combustion with lower excess air, andbetter (or comparable) carbon burnout provide greater thermal efficiencyfor a combustion system fired with the upgraded petroleum coke. Low ashfusion temperatures are not expected to create heat exchange problemsdue to the low-level decontamination to remove sodium and vanadium fromthe petroleum coke to acceptable levels.

[0231] D. Environmental Controls of the Prior Art

[0232] Various technologies currently exist for particulate control andremoval of undesirable pollutants, primarily sulfur oxides SOx. Thepresent invention does not claim these technologies separately, butprovides improvements and novel combinations of these technologies inapplications of the present invention, particularly in retrofitapplications.

[0233] (1) Particulate Control Device (PCD) Fundamentals:

[0234] Particulate emissions from solid-fuel combustion come fromnoncombustible, ash forming mineral matter in the fuel. Additionalparticulates are unburned carbon residues from incomplete combustion ofthe fuel. Though solid particulates from solid-fuel combustion primarilyrange in size from 1-100 microns, finer particulates less than 10microns are the focus of recent environmental concerns. “Bottom ash”refers to larger, heavier particulates that are collected in hoppersbeneath the furnace of the combustion facility. “Flyash” refers to finerash that is entrained in the flue gas and is collected in heatexchange/air preheater hoppers and various types of particulate controlequipment. Traditional particulate control devices (PCDs) forconventional, solid-fuel combustion systems include (but are not limitedto) electrostatic precipitators (ESPs), various types of filteringsystems, mechanical collectors, and wet scrubber systems.

[0235] a. Electrostatic Precipitators (ESP):

[0236] A wide variety of ESP technologies has evolved through the years,including dry and wet versions. The electrostatic precipitatorelectrically charges the particulates in the flue gas to collect andremove them. The ESP is comprised of a series of parallel verticalplates through which the flue gas passes. Centered between the platesare charging electrodes which provide the electric field. The negativelycharged particles are attracted toward the grounded (positive)collection plates and migrate across the gas flow. The chargingelectrodes and collection plates are periodically cleaned by rappingthese components and dislodging sheets of agglomerated particles thatfall into large hoppers. ESPs have low pressure drops due to theirsimple design characteristics. ESP collection efficiencies can beexpected to be 95-99+% of the inlet dust loading. Overall ESPperformance depends on various design and operational factors, including(but not limited to) flyash loading, particle resistivity, particledrift velocity, electric field strength, and the ratio of plate surfacearea to flue gas flow. Lower sulfur concentrations in the flue gas canlead to lower ESP collection efficiency due to their effects on particleresistivity. ESPs are available in a broad range of sizes for utilityand industrial applications.

[0237] b. Fabric Filters:

[0238] Various types of filtering systems have evolved as well. The morepopular types include numerous tubular (or bag) filters in parallel flowarrangements, and have been commonly referred to as baghouses. Baghousesystems usually have multiple compartments with each compartmentcontaining hundreds to thousands of bag filters. The baghouse, or fabricfilter, collects the dry particulates as the cooled flue gas passesthrough the porous filter material that separates the particulate fromthe flue gas. Agglomerated layers of particulates (commonly calledfiltercake) accumulate on the filter material. This filtercakeincreasingly restricts the gas flow, until the filter media is cleaned.Different baghouse technologies have a variety of designs to continuallyclean the filtering media in temporarily inactive compartments: pulsejet, reverse air, shaker and deflation. Fabric filters havesignificantly higher pressure drops than ESPs due to the filter mediaand filtercake. However, power usage of fabric filters and ESPs tend tobe similar because the additional fan power needed to overcome theincreased pressure drop in fabric filters is approximately equal to thepower consumed in the ESP transformer rectifier sets. Fabric filtercollection efficiency can be expected to be 95-99+%. Fabric filters aresubstantially more effective than ESPs in the removal of particulatesless than 2 microns. Overall performance depends on various design andoperational factors, including (but not limited to) flyash loading,gas-to-cloth ratio, pressure drop control, and type/porosity of filtermaterial. Fabric filters are considered to be more sensitive tooperational upsets or various load swings than ESPs due to maximumtemperature and stress limitations of the filter material. Finally,fabric filters have the potential for enhancing SOx capture ininstallations downstream of SOx dry scrubbing or dry sorbent injectionsystems (via longer reagent exposure & reaction residence times in thefilter cake).

[0239] c. Mechanical Collectors:

[0240] Mechanical dust collectors, often called cyclones or multiclones,have been used extensively to remove large particles from a flue gasstream. The cyclonic flow of gas within the collector and thecentrifugal force on the particles drive the larger particles out of theflue gas. Cyclones are low cost, simple, compact and rugged devices.However, conventional cyclones are limited to collection efficiencies ofabout 90% and are poor at collecting the smallest particulates (<10microns). Improvements in small particulate collection requiresubstantially higher pressure drops and associated costs. Consequently,mechanical collectors had been widely used on small combustionfacilities when less stringent particulate emission limits applied.

[0241] d. Wet Scrubbers:

[0242] Finally, various wet scrubber systems have evolved to controlparticulate and other emissions, including sulfur oxides. Wet scrubbingtechnologies for combined particulate and SOx control typically employhigh pressure drop, turbulent mixing devices (e.g. venturi scrubbers)with downstream separation. However, the high energy consumption of thistype of wet scrubber made them impractical for use with largercombustion facilities, particularly modern, utility boilers. Pressuredrops of 10-72 inches of water are necessary for >85% removal ofparticulates down to 0.5-1.0 microns. In contrast, only 0.5-1.5 inchesof water are required to achieve >85% collection of particles >10microns in gravity spray towers. These low pressure-drop, wet scrubberscan achieve some ash particulate control, but are primarily used for thecontrol of sulfur oxides. Particulate sulfur compounds formed in thisprocess are collected in liquid film or droplets.

[0243] (2) Sulfur Oxides (SOx) Control Fundamentals:

[0244] A variety of SOx control technologies are in use and others arein various stages of development. Commercialized flue gasdesulfurization (FGD) processes for solid-fuel, combustion facilitiesinclude (but are not limited to) wet, semi-dry (spray dry adsorption),and completely dry (dry sorbent injection) systems. In all three ofthese system types, alkaline reagent(s) (i.e. compounds of alkali oralkaline earth metals) reacts with the sulfur oxides to form collectiblesulfur compounds. Wet scrubber systems normally have upstreamparticulate control devices (PCDs) to remove any flyash prior to SOxremoval, and collects its sulfur products in a liquid film. In contrast,sulfur products from the spray dry adsorption and dry sorbent injectionsystems are usually collected together with the flyash in downstreamPCDs.

[0245] a. Wet Scrubbers:

[0246] Wet FGD systems have been the dominant worldwide technology forthe control of SOx from utility power plants. In the wet scrubbingprocess, alkaline sorbent slurry is contacted with the flue gas in areactor vessel. The most popular wet scrubber reactor is the spray towerdesign where the average superficial gas velocity is less than thedesign gas velocity at maximum load. Flue gas enters the scrubber moduleat a temperature of 250-350° F., and is evaporatively cooled to itsadiabatic saturation temperature by the slurry spray. The slurryconsists of water mixed with an alkaline sorbent: usually limestone,lime, magnesium promoted lime, or sodium carbonate. Spray nozzles areused to control the mixing of slurry with the flue gas. Sulfur dioxideis absorbed by the liquid droplets and chemically converted to calciumsulfite and calcium sulfate. These wet scrubber reactions usually takeplace in the pH range of 5.5-7.0. The sulfur compounds formed in thisprocess are collected in the liquid film and deposited in the reactiontank at the base of the scrubber. Forced oxidation is often used in thereaction tank to oxidize the collected calcium sulfite to calciumsulfate, which precipitates from the ionic solution. If the calciumsulfate has sufficient purity, it can be used as commercial gypsum (e.g.wallboard manufacture). Unreacted reagents (dissolved in the ionicsolution) are recirculated in the sorbent slurry, increasing sorbentutilization.

[0247] Many factors determine the number of gas phase transfer units(Ng) and SOx removal efficiencies. These factors include slurry sprayrate, slurry droplet size, spatial distributions, gas phase residencetime, liquid residence time, wall effects, and gas flow distribution. Ingeneral, wet scrubbing is a highly efficient SO₂ control technology withremoval levels >90% at stoichiometric calcium/sulfur (Ca/S) ratios closeto 1.0. Primary advantages of this reliable, established technologyinclude (1) high utilization of sorbents and (2) the ability to produceusable products: gypsum or sulfuric acid. The major disadvantages of wetscrubbing are (1) complexity of operation, (2) limited control of sulfurtrioxide (SO₃), (3) potential scaling and corrosion problems, and (4)wet disposal products that typically require dewatering, stabilization,and/or fixation.

[0248] b. Dry Scrubbers:

[0249] Dry scrubbing (sometimes referred to as spray absorption, spraydrying, or semi-wet scrubbing) is the principal alternative to wetscrubbing for SOx control on solid-fuel combustion systems. Dryscrubbing involves spraying a highly atomized slurry or aqueous solutionof alkaline reagent into the hot flue gas to absorb SO₂. Variousalkaline reagents have been used in dry scrubbers, but the predominantreagent used is slaked lime, which behaves like highly reactivelimestone. The quantity of water in the atomized spray is limited sothat it completely evaporates in suspension. SO₂ absorption takes placeprimarily while the spray is evaporating. The dry scrubber reactionsusually take place in the pH range of 10-12.5. Apparently, this highalkalinity contributes to the dry scrubber's effective removal of sulfurtrioxide (SO₃) from the flue gas. The dry scrubber is noted to quenchthe inlet flue gas to a temperature below the dew point for SO₃. Testshave indicated that virtually all S0₃ is absorbed and neutralized in thespray dry absorber. That is, condensed sulfuric acid allegedly reactswith the alkaline sorbent to form a collectible salt.

[0250] SOx dry scrubbers are designed to achieve the appropriatereaction conditions for the specific alkaline reagent used: temperaturezone, mixing, residence time, and moisture. Dry scrubbers are normallysized for a certain gas-phase residence time (typically 8-12 seconds),which depends on the degree of atomization and the design approachtemperature. The approach temperature is the difference between theadiabatic saturation temperature and the temperature of flue gas leavingthe dry scrubber. Dry scrubbers are typically located immediatelydownstream of the air preheater (flue gas temperatures 250-350° F.), andupstream of the particulate control device. The slurry sprayadiabatically cools the flue gas. Consequently, the flue gas temperatureleaving the dry scrubber may be too low for proper operation of theparticulate control device. In these instances, the gases may requireheating before entering the PCD (fabric filter or ESP). An electrostaticprecipitator (ESP) is more forgiving of temperature variation but thebaghouse has the advantage of being a better SOx-lime reactor.

[0251] Dry scrubber performance is primarily dependent upon reagentstoichiometry and approach temperature. SOx removal efficiencies of85-95% can be achieved with stoichiometric Ca/S ratios of 1.2-1.6 withsolids recycle. The primary advantages of dry scrubbing over wetscrubbing include (1) dry waste products, (2) greater S0₃ control, and(3) less costly construction materials. Major disadvantages include (1)high sorbent utilization rates, and (2) potential reheatingrequirements. The high sorbent utilization rates have limited dryscrubber applications to units burning low-sulfur fuel. Dry scrubberscan increase particulate loading to PCDs and waste disposal by 2-4times.

[0252] c. Dry Sorbent Injection:

[0253] Furnace sorbent injection has been developed over the past 20-25years. Dry sorbent technologies do not use reaction chambers, butpneumatically inject alkaline reagents directly into the flue gas at thelocation of appropriate temperatures for the desired reactions. Thesedry sorbent technologies rely on the combustion system to provide themixing and residence time necessary to achieve high conversion levels.These systems cost less, but provide less SOx reduction capabilities.They can also increase particulate loading to PCDs and waste disposal by3-5 times due to low sorbent utilization efficiency. Three major typesof dry sorbent injection appear promising:

[0254] 1. Furnace Injection of Calcium-Based Sorbents: Limestone,dolomite, or hydrated lime readily reacts with SOx in the temperaturerange of 2000-2300° F. Normally, the injection point for these sorbentsis near the nose of the boiler. Using these sorbents, 30-65% SOx removalis achievable with stoichiometric calcium/sulfur (Ca/S) ratios of 2.

[0255] 2. Economizer Inlet and/or Post-Furnace Injection of CalciumHydroxide:

[0256] hydrated calcium hydroxide (Ca(OH)₂) favorably reacts with SOx inthe temperature range of 840-1020° F. Injection of this sorbent at theeconomizer inlet of many boilers can achieve 40-80% SOx capture withCa/S=2. Alternatively, this sorbent can be injected immediatelydownstream of the air heater with an associated humidification systemthat increases relative humidity, approaching the saturationtemperature. With an approach temperature of <50° F., SOx capture of50-55% can be achieved with Ca/S=2. Since the sulfite formation is veryfast (<250 milliseconds) and the reaction window is approximately 212°F. wide, the process is compatible with high quench rates (typically932-1112° F./sec) through economizers.

[0257] 3. Post-Furnace Injection of Sodium-Based Sorbents: Trona andnacholite (naturally occurring forms of sodium carbonate andbicarbonates) react with SOx at air heater exit temperatures (250-350°F.). A relatively simple injection system is placed between the airheater and baghouse. SOx reactions take place in the flue ahead of thebaghouse and on the surface of the fabric filter. However, sodiumcarbonates have been observed to catalyze the oxidation of nitric oxide(NO) to nitrogen dioxide (NO₂), which creates a visible, brown stackplume. SOx removal efficiencies for nacholite are 70-80+% withsodium/sulfur ratio=1 (i.e. NSR =normalized stoichiometric ratio); Tronahas demonstrated 45-70% removal with NSR Na/S=1. In both sorbents, loweroverall removal efficiencies are achieved with ESPs vs. fabric filters.

[0258] d. Other SOx Control Technologies:

[0259] Many other technologies are being evaluated for their potentialcommercial application to address SOx control and acid rainlegislation/regulations. Considerable activity is being devoted thedevelopment of a technology that effectively controls both sulfur oxidesand nitrogen oxides, with high removal efficiencies and operationalreliability. One such technology is particularly relevant to the presentinvention: activated coke beds for SOx and NOx control. The activatedcoke can adsorb SO₂, and catalyze the reduction of NOx by ammonia.Regeneration of the spent coke at high temperature produces aconcentrated SO₂ stream that can be further processed to yield a salableby-product, such as sulfuric acid. Such systems have been commerciallyapplied in Japan and Germany, where S02 removals of 90-99+% and NOxremovals of 50-80+% have been reported. However, most experience hasbeen with low- to medium-sulfur systems. There is some questionregarding process suitability for high-sulfur applications because ofhigh coke consumption.

[0260] e. Retrofit Applications:

[0261] Various types of dry scrubbing and dry sorbent injection systemshave been demonstrated on retrofit utility boiler applications withbaghouses or electrostatic precipitators. These retrofit applicationshave usually added reaction chamber(s) and/or injection system(s)upstream of existing particulate control devices (PCDs) withoutsignificant increases in the PCD capacity. That is, the PCD is not onlyrequired to control ash particulates, but also handle the increased loadof dry particulates resulting from the conversion of sulfur oxides.These dry particulates normally consist of ionic salts; spent sorbentand unreacted sorbent. Typically, these salts are relatively large andeasier to collect than ash particulates. However, the combined load(Mlb/Hr.) can be more than 200% of the original design. Consequently,this type of dry scrubber retrofit can be limited by (1) ash particulateinhibition of reagent reactivity and (2) capacity limiting effect on PCDcollection efficiency. Even so, numerous dry scrubber retrofits havedemonstrated SOx removal efficiencies between 85 and 90% with somesacrifice in particulate emissions. Similarly, dry sorbent injectiontechnologies have been demonstrated on retrofit systems to achieve40-70% with sacrifices in particulate emissions. In general, theserelatively low capital-cost alternatives can effectively reduce sulfuroxide emissions. However, environmental regulations for particulateemissions can be prohibitive for their use as long-term solutions.

[0262] (3) Nitrogen Oxides (NOx) Control Fundamentals:

[0263] Nitrogen oxides emissions are formed in the combustion process bytwo mechanisms: (1) Fuel NOx: oxidation of fuel-bound nitrogen duringfuel devolatilization and char burnout, and (2) Thermal NOx:high-temperature oxidation of the nitrogen in the air. Typically, morethan 75% of the NOx formed during conventional PC firing (i.e. w/o LowNOx Burners) is fuel NOx. Even though fuel NOx is a major factor, only20-30% of the fuel-bound nitrogen is actually converted to NOx inuncontrolled conditions. Both NOx formation mechanisms are promoted byrapid fuel-air mixing, which produces high volumetric heat releaserates, high peak flame temperatures, and excess available oxygen.However, thermal NOx is far more sensitive to high flame temperatures,particularly >2200° F. The potential reduction of nitrogen oxides (NOx)emissions is site specific and depends on various combustion design andoperational factors.

[0264] a. Combustion Modifications:

[0265] Low NOx burners, staged combustion, flue gas recirculation, andreburning are various types of combustion modifications used to controlthe rate of fuel-air mixing, reduce oxygen availability in the initialcombustion zone, and decrease peak flame temperatures. These combustiontechniques can be used separately or in combination to reduce thermaland fuel NOx. NOx reductions from these methods typically range from 20to over 60%. Low NOx burners slow and control the rate of fuel-airmixing, thereby reducing oxygen availability and peak flame temperaturesin the ignition and primary combustion zones. Staged combustion uses lowexcess air levels in the primary combustion zone with the remaining(overfire) air added higher in the furnace to complete combustion. Fluegas recirculation reduces oxygen concentrations and combustiontemperatures by recirculating some of the flue gas to the furnacewithout increasing total net gas mass flow. In reburning, 75-80% of thefurnace fuel input is burned in Cyclone furnaces with minimum excessair. The remaining fuel (gas, oil, or coal) is added to the furnaceabove the primary combustion zone. This secondary combustion zone isoperated substoichiometrically to generate hydrocarbon radicals whichreduce NOx formed in the Cyclone to molecular nitrogen (N₂). Thecombustion process is then completed by adding the balance of thecombustion air through overfire air ports in a final burnout zone in thetop of the furnace.

[0266] b. Selective Non-Catalytic Reduction (SNCR):

[0267] In SNCR, ammonia or other compounds (e.g. urea) that thermallydecompose to ammonia are injected downstream of the combustion zone in atemperature region of 1400 to 2000° F. If injected at the optimumtemperature, the NOx in the flue gas reacts with the ammonia to producemolecular nitrogen (N₂) and water. Without base-load operation, locatingammonia injection system(s) at the optimal temperature is somewhatdifficult due to temperature variations with load swings and operationalupsets. The injection of hydrogen, cyanuric acid, or ammonium sulfate issometimes used to broaden the effective temperature range. NOx reductionlevels of 70% (from inlet concentrations) are possible under carefullycontrolled conditions. However, 30-50% NOx reductions are more typicallyused in practice to maintain acceptable levels of reagent consumptionand unreacted ammonia carryover. Unreacted ammonia (often called ammoniaslip) can (1) represent additional pollutant emissions and (2) createammonium sulfate compounds that deposit on downstream heat exchangesurfaces and cause plugging, fouling, and corrosion problems.

[0268] c. Selective Catalytic Reduction (SCR):

[0269] SCR systems remove NOx from flue gases by reaction with ammoniain the presence of a catalyst to produce molecular nitrogen (N₂) andwater. Most SCR units can operate within a range of 450-840° F, butoptimum performance occurs between 675 and 840° F. The minimumtemperature varies and is based on fuel, flue gas specifications, andcatalyst formulation. NOx control efficiencies of 70-90% can beconsistently achieved. Like SNCR, these control efficiencies aredependent on inlet NOx concentrations, and are cumulative to NOxreductions from combustion modifications. Also, the same concerns forunreacted ammonia exist in SCR units.

[0270] d. Other NOx Control Technologies:

[0271] Other technologies are being evaluated for their potentialcommercial application to address NOx control and acid rainlegislation/regulations. Considerable activity is being devoted thedevelopment of a technology that effectively controls both nitrogenoxides and sulfur oxides, with high removal efficiencies and operationalreliability. Most involve variations of reducing NOx with ammonia,similar to SNCR and SCR. As noted above, activated coke technology forthe removal of SOx and NOx is particularly relevant to the presentinvention.

[0272] (4) Carbon Dioxide (CO₂) Control Fundamentals:

[0273] Environmental concerns of global warming have only recentlytargeted carbon dioxide (CO₂) as a flue gas component that needs to becontrolled. Consequently, control technologies for carbon dioxide arecurrently in various stages of development. Wet scrubbing and flue gasconversion to collectible particulates are being evaluated for low-levelcontrol methods. High-efficiency technologies include physicaladsorption on activated media, chemical solvent stripping, cryogenicfractionation, membrane separation, and direct recovery from flue gasrecirculation with I₂/CO₂ combustion. Unfortunately, the disposal ofproducts from high-efficiency, non-regenerative control processesbecomes prohibitive due to the high levels of CO₂ in the flue gas.Consequently, most of the technologies are regenerative producing ahighly concentrated CO₂ waste stream. Different sequestering methods arebeing evaluated including deep ocean injection, oil well injection, andbiological fixation.

[0274] a. Wet Scrubbing:

[0275] Various types of reagents are being tried in conventional wetscrubbing systems. Limited information and data have been published todate.

[0276] b. Conversion to a Dry, Collectible Particulate:

[0277] Another approach being pursued is the, conversion of CO₂ to a dryparticulate upstream of a particulate control device. The alkalinereagents that convert sulfur oxides to dry particulates are not aseffective for carbon dioxide. Carbon dioxide does compete with sulfuroxides for reactions with some SOx dry scrubber reagents to a limitedextent, and minor reductions are achieved. However, carbon dioxide ismore stable and is expected to require a much stronger reagent, such asammonia, sodium hydroxide, and calcium hydroxide. At this point,concurrent conversion of both sulfur oxides and carbon dioxide toparticulate does not appear likely due to a lack of reagent preferenceor selectivity for carbon dioxide. Different temperature windows,residence times, and reagents may be necessary. Consequently, conversionof carbon dioxide to dry particulates may require independent systemswith different reagents, unless the fuel generates low levels of sulfuroxides.

[0278] c. Adsorption on Activated Media:

[0279] The physical adsorption of CO₂ on activated carbon or zeolitesystems is a surface phenomena in which a few layers of the adsorbed gasare held by weak surface forces. The capacity of an adsorbent for agiven gas depends on the operating temperature and pressure. The keyissue for commercial application of these systems is the surface arearequired per unit of mass or volume of adsorbed gas. However, thesesystems are simple; their operation and regeneration (pressure swing ortemperature swing) can be energy-efficient.

[0280] (5) Air Toxics Control Fundamentals:

[0281] Prior to the Clean Air Act Amendments (CAAA) of 1990, EPA airtoxics standards had been promulgated for only seven hazardous airpollutants. In the CAAA's Title IlIl, EPA was required to promulgatecontrol standards for over 189 air toxic substances. Consequently,control technologies for air toxics are currently in various stages ofdevelopment. Adsorption on activated carbon, wet scrubbing, and flue gasconversion to collectible particulates are three primary classes oftechnologies being considered.

[0282] (6) Solid Waste Control Fundamentals:

[0283] Solid wastes from fossil fuel combustion systems was originallyexcluded from Subtitle C of the Resource Conservation & Recovery Act(RCRA) of 1976, and still requires clarification by U.S. federalregulations. In the meantime, high volume waste streams from powerplants, such as scrubber sludge, flyash, and bottom ash are subject todifferent and highly variable disposal requirements from state and localenvironmental and health authorities. In addition, many landfills arerequired to use leachate collection systems with single or doublelinings and extensive monitoring wells. In some cases, stabilization ofthe solids is required.

[0284] a. FGD Wet Scrubber Sludge:

[0285] In order to dispose of waste materials from wet collectionsystems, treatment methods are applied to ultimately produce a solid.Dewatering, stabilization, and fixation are common treatment methodsthat are designed to achieve waste volume reduction, stability, betterhandling, and/or liquid recovery for reuse. Dewatering techniquesphysically separates water from solids to increase solids content, andinclude settling ponds, thickeners, hydroclones, and vacuum filters.Stabilization further increases solids content of the waste by addingdry solids, such as flyash. Fixation involves the addition of an agent,such as lime, to produce a chemical reaction to bind free water andproduce a dry product.

[0286] b. Dry Solid Wastes:

[0287] Ultimate disposition of utility plant wastes (bottom ash, flyash,FGD residues, etc.) is by utilization or by disposal inlandfills/impoundments. Utilization may be environmentally preferred andbecomes more attractive as waste management costs increase. In somecases, bottom ash and boiler slag can be substituted for sand, gravel,blasting grit, roofing granules, and controlled fills. Flyash can alsobe utilized in the manufacture of Portland cement and concrete mixes, ifit meets certain minimum quality specifications. In all utilizationalternatives, the cost of transportation can be prohibitive. Disposalmethods can be either wet or dry, depending on the physical condition ofthe waste materials. The trend is toward dry disposal because of smallervolumes, more options for site and material reclamation, and thedeveloping interest in dry scrubbing. Dry disposal can use a simplemethod of landfill construction in which the waste is placed andcompacted to form an artificial hill.

[0288] E. Environmental Control of the Present Invention

[0289] The present invention does not claim the prior art environmentalcontrol technologies separately, but provides improvements and novelcombinations of these technologies in applications of the presentinvention. The different combinations of these technologies are somewhatinvolved and provide synergism and/or unappreciated advantages that arenot suggested by the prior art.

[0290] In most cases, fuel switching to the premium “fuel-grade”petroleum coke of this invention provides the opportunity forsubstantial improvements in the control of particulates, sulfur oxides(SOx), nitrogen oxides (NOx), carbon dioxide (CO₂), air toxics, andopacity. In Table 2-B, uncontrolled pollutant emissions of upgradedpetroleum cokes are compared to the emissions of various types of coal.The total quantity of undesirable flue gas components (e.g. SOx) istypically lower than coals', even with higher component concentration inthe fuel (wt. % in pet coke vs. coal). That is, sulfur, nitrogen, andcarbon contents of the upgraded coke are normally comparable or higher.Most of these potential reductions in uncontrolled pollutants arerelated to the significantly lower fuel rates and ash content of theupgraded petroleum coke. In particular, the dramatic reduction in ashparticulates (>90%) creates tremendous excess capacity in the existingparticulate control device. This excess capacity can be effectively usedto collect other pollutants that have been converted to collectibleparticulates upstream of the PCD. Finally, none of these environmentalimprovements would be possible without the fuel properties of the newformulation of petroleum coke that allows utility boilers to burn up to100% of this premium fuel.

[0291] (1) Conversion of Existing Particulate Control Devices:

[0292] The predominant environmental control feature in the presentinvention is the potential use of existing particulate control equipmentfor the control of sulfur oxides (SOx) and other undesirable flue gascomponents. Since petroleum coke typically has >90% less ash than mostcoals (i.e. 0.1-0.3% vs. 5-20%), a0 tremendous amount (90-95+%) ofparticulate control capacity in existing particulate control devices ismade available by fuel switching (i.e. from coal to the upgradedpetroleum coke). As such, existing particulate control devices(baghouses, ESPs, etc.) can be used for extensive removal of undesirableflue gas components by converting them to collectible particulatesupstream of these devices.

[0293] The present invention can further increase the capacity of theexisting particulate control device by substantially reducing fuelrates. That is, the upgraded petroleum coke has 10-200+% greater heatingvalue than most coals, which translates into 10-50+% reduction in fuelrates to achieve the same heat release rate. The lower fuel rates andthe associated reductions in air flow rates o f t e n providesignificant reductions in flue gas flow rates. In an existing combustionsystem, any significant reduction in flue gas flow rate increases fluegas residence time, PCD capacity, and PCD control efficiency. Theseperformance parameters are strongly related to the flue gas flow rateand velocities through the PCD collection media. For example, the ratioof ESP plate area to volumetric flue gas flow rate is a criticalparameter in the Deutsch-Anderson Equation, which determines ESPcapacity and control efficiency. Similarly, the air-to-cloth ratio(where air=flue gas flow in combustion sources) is a critical parameterin equations that determine fabric filter capacity and controlefficiency. In this manner, the control efficiency in the existing PCDis increased, providing a greater capacity to control higher inletloadings to the same particulate requirements for PCD outlet.

[0294] Each combustion system will have a different set of designconditions for converting the existing particulate control devices. Theconversion of each system will depend on various design and operationalparameters, but the optimal design and level of control can beestablished with typical engineering skills associated with the priorart of PCD technologies. Minor modifications may be necessary tomaintain particulate collection efficiencies. The particulates cominginto the existing PCDs may have substantially different properties thanthe particulates of the PCD's design basis. Consequently, modestmodifications in design and/or operating conditions may be required. Forexample, flue gas conditioning or operational changes in existing ESPsmay be appropriate to achieve more desirable resistivitycharacteristics, and maintain collection efficiencies.

[0295] (2) Flue Gas Conversion Technologies:

[0296] The present invention includes the integration of various “fluegas conversion technologies” to control undesirable flue gas components,and effectively use the excess particulate control capacity created bythe present invention. For the sake of this discussion, “flue gasconversion technologies” refers to all technologies that convert gaseousor liquid compounds in the flue gas into chemical compounds (e.g. dry orwet particulates) that can be effectively collected by particulatecontrol technologies (existing, new, or otherwise). Most of thesetechnologies inject a chemical reagent (wet or dry) that reacts with thetargeted flue gas component(s) and chemically converts them tocompound(s) that are particulates at the PCD operating conditions.Consequently, this classification of environmental controls wouldinclude commercially available SOx controls: wet scrubbing, spray dryadsorption, and dry sorbent injection. The present invention providesnovel use and improvements in these and other flue gas conversiontechnologies because of its unique ability to (1) improve the reagentactivity and utilization efficiency, (2) provide the opportunity forreagent regeneration (and associated improvements), (3) increase theprobability of salable by-products, and (4) promote the development ofimproved and new flue gas conversion technologies (FGCT).

[0297] a. Reagent Activity & Utilization Efficiency:

[0298] The present invention provides less ash interference and betterrecycle options to increase the reagent activity and utilizationefficiency in FGC processes. In many situations, the flyash from thecombustion process interferes with the reactions of reagent and targetedflue gas component. The upgraded petroleum coke of the present inventionhas very low ash content, which substantially reduces interference andincreases reagent activity. This much lower flyash also allows extensiverecycling of conversion products, including unreacted reagents. Forexample, the prior art in SOx dry scrubber technology processes andrecycles collected flyash into the reagent injection to increase reagentusage. However, high ash particulates of existing fuels limit the degreeof recycling. The upgraded petroleum coke of the present invention hassuch low ash particulates that greater quantities of collected flyash(mostly FGCT products and unreacted reagents) can be effectivelyrecycled. The degree of recycle can be limited by the capacity of thePCD, but recycle rates of 5-30+% are possible. The optimal recycle ratecan be developed for each application. Both the reduced ash interferenceand the improved recycle capabilities are expected to significantlyincrease reagent utilization efficiencies and improve FGCT overallcontrol efficiencies and costs.

[0299] b. Opportunity for Reagent Regeneration:

[0300] The present invention provides the opportunity for regenerationof FGCT reagents, due to very low ash and other impurities in thecollected flyash. That is, the collected flyash consists mostly of FGCTproducts (or spent reagent) and unreacted reagent. The collected flyashcan be processed, and the spent reagent can be regenerated tosubstantially reduce the make-up FGC reagent rate and waste disposalrequired. The regeneration process can include, but should not belimited to, hydration of the collected flyash and subsequentprecipitation of the undesired ions (i.e. sulfates, carbonates, etc.)for commercial use or disposal. Furthermore, the regeneration processwould likely include a purge stream of <30% (in some cases <5%) toremove unacceptable levels of impurities from the system. This purgestream would be analogous to blow down streams in many boiler water andcooling water systems. In many cases, this purge stream will contain ahigh concentration of heavy metals, including vanadium. Various physicaland/or chemical techniques can be used to extract and purify thesemetals for commercial use. In cases where slaked lime is used as theconversion reagent, the regeneration process can also greatly reduce thecarbon dioxide generated in the reagent preparation process: limestone(calcium carbonate—CaCO₄) to lime (calcium oxide—CaO)+carbon dioxide(CO₂). Finally, the ability to continually regenerate reagents providesthe opportunity for new or improved flue gas conversion processesthrough the use of exotic reagents; not considered previously due tocosts. In this manner, the regeneration of conversion reagents can (1)substantially reduce reagent make-up and preparation costs (2)dramatically reduce flyash disposal costs, (3) create a resource forvaluable metals, (4) reduce CO₂ emissions, and (5) provide the means toeconomically improve the flue gas conversion process via the use of moreexotic reagents.

[0301] c. Salable By-Products:

[0302] Whether or not the FGCT reagent is regenerated, the presentinvention increases the probability of producing salable by-products.The extremely low ash particulate levels create a collected flyash thatis mostly FGCT reaction products with low impurities. As such, collectedflyash from certain FGCTs can be used as raw materials for variousproducts, instead of solid wastes requiring disposal. These productsinclude, but are not limited to, gypsum wallboard and sulfuric acid.

[0303] d. Development of Improved and New Conversion Technologies:

[0304] The present invention can promote novel improvements anddevelopment of many flue gas conversion technologies. Regeneration withexisting reagents can be developed for improvements of the currentsulfur oxides conversion technologies. Furthermore, all these uniqueabilities of the present invention (i.e. efficient reagent utilization,reagent regeneration, and salable by-products) contribute to thedevelopment of new flue gas conversion technologies for any undesirableflue gas components, including sulfur oxides, carbon dioxide, nitrogenoxides, and air toxics. The unique ability to regenerate conversionreagents, in particular, opens the door to more exotic reagents that aremore reactive, selective, and/or costly to prepare. In the past, reagentselection has been limited to very inexpensive materials due todisposable nature (i.e. use once & throw away). With dramatically lowerimpurities in the system, regeneration using novel conversion reagentscan be economically considered. That is, other alkaline metal compoundswith more desirable reaction characteristics or by-products can be usedwithout major economic consequences. For example, ammonia and veryreactive hydroxide forms of magnesium, sodium, and/or calcium can beeconomically used as reagents in FGCTs to control carbon dioxide,nitrogen oxides, and/or air toxics. In addition, transportation costsfor make-up reagent and waste disposal can be dramatically reduced andhelp offset other additional costs (e.g. regeneration system costs).

[0305] The integration of these flue gas conversion technologies isanticipated by the present invention. That is, part of the benefits ofthe present invention is to create excess particulate control capacityin existing combustion systems that can be used in conjunction withthese technologies to achieve their objectives. In this manner, Thepresent invention provides a novel combination of particulate controland flue gas conversion technologies, particularly in retrofitapplications on existing combustion systems. These novel combinedapplications of existing environmental technology provide substantialincentives to replace existing solid fuels with the upgraded petroleumcoke. However, each combination of particulate control and flue gasconversion technologies at existing combustion systems is a uniqueapplication. One skilled in the art of these technologies is capable ofproviding the appropriate design and operating modifications required toachieve the successful implementation of the desirable application ofthese combined air pollution control technologies.

[0306] F. Environmental Impacts of an Exemplary Embodiment

[0307] In an exemplary embodiment of the present invention, an existingutility boiler with a particulate control device is modified by fuelswitching: existing coal to premium “fuel-grade” petroleum coke. Theupgraded petroleum coke of the present invention can be fired as theprimary fuel (up to 100%). Consequently, the very low ash particulatelevel generated from such a fuel switch unleashes >90% of the existingPCD's capacity to be used for flue gas conversion technologies (FGCT).

[0308] In this embodiment, two options are provided for the novelintegration of existing FGCT for the control of sulfur oxides. Sulfuroxides control was chosen in this embodiment due to recent emphasisrelated to acid rain legislation. However, FGCT for other undesirableflue gas components can be implemented in a similar manner. Option 1consists of the addition of retrofit reaction chamber(s) and reagentinjection system(s) to convert sulfur oxides to dry particulatesupstream of the existing particulate control device(s). Alternatively,Option 2 consists of the addition of dry sorbent injection systems intoand/or downstream of the furnace section to convert sulfur oxides (orcarbon dioxide) to dry particulates upstream of the existing particulatecontrol device(s). An optimized combination of Options 1 and 2 canprovide the desired SOx control system in many cases (See OptimalEnvironmental Control Embodiment).

[0309] As noted previously, all of these applications of flue gasconversion technology (including SOx controls) are novel and unlike anyother commercial, retrofit applications. First, most flue gas conversionapplications have substantially higher ash particulates in the flue gas.The ash particulates can interfere with the reactivity of the injectedreagents, potentially decreasing SOx removal efficiencies. Secondly,previous utility retrofit applications have used existing PCDs that arestill operating at >80% of capacity for ash collection and sacrificeparticulate emission levels. In contrast, the existing PCDs in thisapplication are operating at <10% of capacity for ash collection. Thisdesign basis provides the opportunity to achieve much higher SOxremoval, while increasing (or maintaining) collection efficiency in thePCD. Consequently, particulate emissions from the stack aresignificantly less (or comparable). Finally, the very low ashparticulates cause the particulates collected by the PCD to bepredominantly spent reagent and unreacted reagent. The very low ash andchloride content in the collected particulates provides a greaterability to regenerate spent reagent (e.g. via hydration) and/or recycleunreacted reagent from the collected particulates. Consequently,substantially lower quantities of solids disposal (e.g. purge stream)and fresh reagents for make-up requirements are expected. Alternatively,the collected ash can have sufficient purity to be used in theproduction of sulfuric acid, gypsum wallboard, or other sulfate-basedproducts. This alternative system design can also substantially reducethe solids disposal quantities. In conclusion, the combination of thesefactors makes this application unique, and produces greater operatingefficiencies and more favorable economics.

[0310] The ultimate level of additional control for SOx and particulateswill depend on (1) the efficiency of conversion of the sulfur oxides toparticulates and (2) the efficiency of particulate collection. In mostutility boilers, reductions of over 70% in both sulfur oxides and ashparticulate emissions are expected.

[0311] (1) Particulate Impact:

[0312] The upgraded petroleum coke of the present invention normally hasover 90% less ash particulate emissions than most coals for the samefiring rate (See Table 2-B). This dramatic reduction in ash particulatesis primarily due to a much lower ash content (0.1-1.0 wt. %). However,lower fuel rates (due to significantly higher heating values) can alsocontribute greatly to this reduction. The dramatic reduction in ashparticulates unleashes >90% of the capacity in the existing particulatecontrol device. This excess capacity can be used to collect otherpollutants that have been converted to collectible particulates upstreamof the PCD. In this manner, the fuel properties of the new formulationof petroleum coke provide the opportunity to burn 100% petroleum cokeand use existing particulate control devices to reduce the emissions ofother pollutants, such as sulfur oxides, nitrogen oxides, carbondioxide, air toxics, etc.

[0313] In an exemplary embodiment, the overall particulate emissionsfrom the stack will depend on the ability to maintain high collectionefficiencies in the PCD. As noted above, the type and quantity ofparticulates will be different due to fuel switching and flue gasconversion technologies. For example, the converted salts from the SOxdry scrubbing are normally larger and easier to collect than ashparticulates. Even though the ash particulates are decreaseddramatically, some breakthrough of converted salts from flue gasconversion is expected. The quantity of breakthrough will depend on thedegree of flue gas conversion, unreacted reagents, and the newcollection efficiency. Besides the increase in collection efficiency dueto lower flue gas flow rates, the products from SOx FGCT typically havecharacteristics that increase particulate collection efficiency. Forexample, the resistivity and drift velocity of calcium sulfate favorincreased ESP collection efficiencies. Though the application of FGCTsand utilization of PCDs will vary substantially, the reduction inoverall particulate emissions from the stack is still expected to beover 10%, in most cases. A significant reduction in PM-10 particulate(i.e. <10 microns) emissions is also expected.

[0314] (2) Sulfur Oxides Impact:

[0315] The predominant feature in this exemplary embodiment is thepotential use of existing particulate control equipment for the controlof sulfur oxides (SOx). Since petroleum coke typically has >90% less ashthan most coals (0.1-0.3% vs.

[0316] 20%), a tremendous amount (90-95+%) of particulate controlcapacity in existing particulate control devices is made available byfuel switching (from coal to the upgraded petroleum coke). As such, theexisting particulate control devices (baghouses, electrostaticprecipitators, etc.) can be used for extensive SOx removal by convertingthe sulfur oxides to dry particulates upstream of these devices.

[0317] In Option 1 of the exemplary embodiment of this invention,retrofit reaction chamber(s) and reagent injection system(s) are addedto convert sulfur oxides to dry particulates upstream of the existingparticulate control device(s). As noted previously, 85-95% SOx removalhas been demonstrated by past utility retrofits of SOx dry scrubbersystems with substantially higher ash particulates in the flue gas. Forreasons noted above, the SOx dry scrubber retrofit in the exemplaryembodiment is expected to perform much better. Consequently, 90% SOxremoval efficiency is expected to be a very conservative estimate forthe potential reduction of SOx emissions from the upgraded petroleumcoke and Option 1 SOx control of the exemplary embodiment.

[0318] In Option 2 of the exemplary embodiment, dry sorbent injectionsystems are added to convert sulfur oxides to dry particulates upstreamof the existing particulate control device(s). As noted previously,40-70% SOx removal has been demonstrated by past utility retrofits ofSOx dry sorbent injection systems with substantially higher ashparticulates in the flue gas. For reasons noted above, the dry sorbentinjection retrofit in the exemplary embodiment (Option 2) is expected toperform much better. Consequently, 70% SOx removal efficiency isexpected to be a very conservative estimate for the potential reductionof SOx emissions from the upgraded petroleum coke and Option 2 SOxcontrol of the exemplary embodiment.

[0319] In the past, the presence of vanadium has caused concern ofelevated dew points in the flue gas, due to its tendency to catalyze theconversion of sulfur dioxide to sulfur trioxide. In many situations,these elevated dew points can lead to increased cold-end corrosion.However, the elevated dew points can have positive impacts in theapplication of SOx flue gas conversion processes. That is, the elevateddew points can provide more favorable approach temperatures; improvingcollection efficiencies while reducing water injection requirements.This is particularly helpful in applications where the operatingtemperature of the existing PCD is above the flue gas dew point;reducing the need for flue gas reheat. In addition, tests have shownthat SOx dry scrubbing techniques perform better on sulfur trioxide (vs.sulfur dioxide). Thus, the dry sorbent injection (Option 2), to someextent, can be particularly beneficial to convert sulfur trioxide toparticulates in the convection section. In this manner, the presence ofvanadium can be advantageous upstream of low-temperature heat exchangeequipment. At the same time, the catalytic conversion of SO₂ to SO₃ isalso expected to inhibit the formation of the highest oxidation level ofvanadium; vanadium pentoxide (V₂O₅). This reduction of vanadiumpentoxide further reduces associated ash problems. Finally, infacilities with electrostatic precipitators, the sulfur trioxide canalso condition the flue gas and alter the resistivity characteristics toimprove the ESP's collection efficiency. Consequently, certain levels ofvanadium can improve the SOx control systems.

[0320] The overall reduction of sulfur oxides due to fuel switching andthe retrofit flue gas conversion system is site specific and depends onseveral factors. First, the lower fuel rates of the upgraded petroleumcoke can be sufficient to reduce SOx emission rates (Mlb/Hr. orMlb/MMBtu). This can occur even in cases where the sulfur content (wt.%) of the upgraded petroleum coke exceeds the sulfur content of the coalbeing replaced. Secondly, the sulfur content of the upgraded petroleumcoke can be lower than the sulfur content of the replaced fuel. Forexample, low-sulfur petroleum coke or desulfurized petroleum coke fromhydrotreated coker feedstocks can have significantly less sulfur (wt.%). In these cases, the lower sulfur content, combined with lower fuelrates, contributes to even greater reductions in sulfur oxides. Finally,the retrofit of SOx dry scrubbing technology, in this exemplaryembodiment, is expected to reduce the inlet SOx emission rates by 90% ormore. If the alternative dry sorbent injection systems are used, theinlet SOx emission rates are expected to be reduced by up to 70%. Insome cases, the lower fuel rate and the sulfur content of the upgradedpetroleum coke are not sufficient to reduce the SOx emission rate of thereplaced fuel. However, the combination of the lower fuel rate and theretrofit dry scrubbing can still produce substantially lower SOxemissions (relative to various coals), even when the coke sulfur contentis much higher.

[0321] (3) Nitrogen Oxides Impact:

[0322] The upgraded petroleum coke of the present invention usually hassignificantly less fuel-bound nitrogen due to the combination of lowerfuel rates and comparable nitrogen content, typically 0.5-1.5%. Thus,the fuel NOx is expected to be significantly less or at least similar.Also, the flame intensity (and temperature profile) of the upgraded cokeis expected to be more uniform due to lower VCM content and levelizedburning profile. This uniform temperature profile is expected to producelower Thermal NOx than most coals. The more uniform fuel characteristicsof the upgraded petroleum coke is also expected to reduce excess airrequirements, which lowers oxygen availability and typically lowers bothfuel NOx and thermal NOx. These and other combustion characteristics arealso conducive for the development of lower generation of nitrogenoxides (NOx) emissions through Low NOx burner designs and othercombustion modifications. Consequently, the upgraded petroleum coke ofthe present invention is expected to significantly decrease the nitrogenoxide emissions of most coals, via fuel switching and appropriateadjustments in Low NOx burner design and operation.

[0323] The application of SNCR, SCR, and/or FGCT for NOx is notanticipated in this exemplary embodiment. However, if regulationsrequire additional NOx control, these technologies can be integratedinto the control alternatives of the exemplary embodiment. The majorconcerns in the integration process are the control priorities amongpollutants and the potential conflicts with other control technologies.That is, competitive or other undesirable reactions (e.g. formation ofammonium bisulfate) can be counterproductive in the combination ofcontrol technologies.

[0324] (4) Carbon Dioxide Impact:

[0325] Significant reductions in carbon dioxide emissions can beachieved by methods similar to those for sulfur oxides emissions. First,the carbon content of the upgraded petroleum coke can be lower than thecarbon content of the replaced fuel, but not normally. Secondly, thelower fuel rates in most applications can cause lower carbon dioxideemission rates. This can occur even in cases where the carbon content(wt. %) exceeds the carbon content of the coal being replaced. As shownin Table 2-B, this occurs in almost every case. Finally, a retrofit,flue gas conversion system can be used for modest to moderate carbondioxide control, as well. The combination of these factors willdetermine the overall reduction in carbon dioxide resulting from fuelswitching and the retrofit, flue gas conversion system of the exemplaryembodiment. The potential for reduction from the retrofit CO₂ flue gasconversion is the most uncertain at this time.

[0326] An exemplary embodiment can effectively be used for flue gasconversion of carbon dioxide, if and when the appropriate temperature,residence time, and reagents become better understood and available. Asnoted previously, flue gas conversion of carbon dioxide is more likelywithout concurrent scrubbing of sulfur oxides. Low-sulfur, petroleumcoke, such as desulfurized coke, can effectively improve the opportunityfor carbon dioxide conversion and collection. Table 2-A shows thedesirable fuel properties of desulfurized coke relative to various typesof coals. Alternatively, Option 2 dry sorbent injection system(s) can beused for sulfur oxides control and the Option 1 retrofit reactionchamber(s) and reagent injection system(s) can be used for the controlof carbon dioxide. In this case, the excess capacity of the existingparticulate control device can be the limiting factor. Additional PCDcapacity can be added as part of the retrofit project to increase thecarbon dioxide removal via flue gas conversion processes.

[0327] (5) Air Toxics Impact:

[0328] The regulations regarding the levels of control required forspecific air toxics are still fairly unclear for utility boilers. Ingeneral, though, the upgraded petroleum coke of the present invention isexpected to create less air toxic compounds, due to its much lower ashcontent. This assumes that the combustion process can achieve a highlevel of combustion efficiency and destroy any hydrocarbon, classifiedas an air toxic compound. Flue gas conversion technologies for air toxiccompounds can also be integrated, as necessary. Similar to other FGCTs,the major concerns of integrating these processes are the controlpriorities among pollutants and the potential conflicts with othercontrol technologies.

[0329] (6) Opacity Impact:

[0330] Opacity is an indication of the level of transparency in the fluegases exiting the smokestack or the plume after moisture dissipation.The level of opacity is primarily dependent on (1) particulateconcentration, (2) particle size distribution, (3) sulfur trioxideconcentration, and (4) moisture level. The use of upgraded coke in thisembodiment with either Option 1 or 2 for SOx control is expected tosignificantly reduce the opacity level in most utility boilers, due tothe reductions in particulate and sulfur trioxide concentrations in theflue gases, described above. The reduced moisture and hydrogen contentof the upgraded petroleum coke (vs. most coals) can also contribute tolower opacity and steam plumes. Finally, significant reductions inparticulates less than 10 microns can substantially improve the opacity.

[0331] (7) Solid Waste Impact:

[0332] As discussed previously, the upgraded petroleum coke of thepresent invention can dramatically reduce the quantity and quality ofthe solid wastes for disposal. The upgraded petroleum coke has such lowash particulates that greater quantities of collected flyash can beeffectively recycled to increase reagent utilization efficiencies. Theimproved reagent utilization often creates greater proportions of theflyash as more stable compounds. For example, the fully oxidized, spentreagent in SOX FGCT (calcium sulfate) may be preferred for wastedisposal (versus unreacted reagent or less oxidized forms). Furthermore,the extremely low ash particulate levels (i.e. low impurities) providegreater opportunity to use the collected flyash as raw materials forvarious products, instead of solid wastes, requiring disposal. Theseproducts include, but are not limited to, gypsum wallboard and sulfuricacid. In addition, the spent reagent can be regenerated to dramaticallyreduce the wastes requiring disposal. In this manner, flyash disposaland associated costs are significantly reduced.

[0333] (8) General Issues:

[0334] Finally, none of these environmental improvements would bepossible without the fuel properties of the new formulation of petroleumcoke that allows the utility boilers to burn up to 100% of this premiumfuel. That is, the fuel properties of the upgraded petroleum cokeprovide self-sustained combustion. Without it, these environmentalimprovements would not be possible. The following case study providesjust one example of the benefits that can be achieved with an exemplaryembodiment of this invention.

G. EXAMPLE 1 Utility Boiler with Conventional Particulate Control Device(PCD)

[0335] A power utility has a conventional, pulverized-coal fired,utility boiler that currently burns medium-sulfur, bituminous coal fromcentral Ohio. The existing utility currently has a typical particulatecontrol device with no sulfur oxide emissions control. Full replacementof this coal with a high-sulfur petroleum coke produced by the presentinvention would have the following results:

[0336] Basis=1.0×10⁹ Btu/Hr Heat Release Rate as Input FuelCharacteristics Results Current Coal Upgraded coke VCM (% wt) 40.0 16.060% Lower Ash (% wt.) 9.1 0.3 97% Lower Moisture (% wt.) 3.6 0.3 92%Lower Sulfur (% wt) 4.0 4.3  8% Higher Heating Value (MBtu/lb) 12.9 15.319% Higher Fuel Rate (MIb/Hr) 77.8 65.4 16% Lower

[0337] Pollutant Emissions: Uncontrolled/Controlled Ash Particulates(lb/MMBtu or MIb/Hr) 7.1/0.4 .2/.01 97% Lower Sulfur Oxides (lb/MMBtu orMIb/Hr) 6.2/6.2 5.6/.6 90% Lower Carbon Dioxide (lb/MMBtu or MIb/Hr) 238210 12% Lower

[0338] This example demonstrates major benefits from the application ofthe present invention. The upgraded petroleum coke has substantiallylower ash and moisture contents, compared to the existing coal. Thesefactors contribute greatly to (1) the ability to burn successfully withlower VCM and (2) a fuel heating value that is 19% higher. In turn, thehigher heating value requires a 16% lower fuel rate to achieve the heatrelease rate basis of one billion Btu per hour in the boiler. As notedpreviously, this lower fuel rate and the softer sponge cokesignificantly reduce the load and wear on the fuel processing system,while increasing the pulverizer efficiency and improving combustioncharacteristics.

[0339] The ash particulate emissions (ash from the fuel) are 97% lowerthan the existing coal, due to the lower ash content and higher fuelheating value. In this manner, fuel switching to the upgraded cokeunleashes 97% of the capacity in the existing particulate controldevice. This excess capacity can now be used for the control of sulfuroxides via retrofit flue gas conversion technology.

[0340] A SOx dry scrubber injection/reaction vessel (option 1) is addedupstream of the existing particulate control device, along with anyassociated reagent preparation and control systems. This conversion ofthe existing particulate control device is assumed to achieve 90%reduction in sulfur oxides in this case. Consequently, the uncontrolledsulfur oxide emissions are reduced from 5.6 to 0.56 thousand pounds perhour. In this manner, the utility of switching fuels and converting theexisting particulate control device to dry scrubbing represents 90%reduction in the coal's sulfur oxides emissions (i.e. <0.6 vs. 6.2lb/MMBtu). This unexpected result is achieved even though the sulfurcontent (4.3%) of the upgraded petroleum coke is 8% higher than thesulfur level (4.0%) of the Ohio bituminous coal.

[0341] Alternatively, the dry sorbent injection systems (option 2) couldbe used for sulfur oxides control. In this case, the inlet SOx would bereduced by 70% (i.e. 5.6 to 1.7 Lb/MMBtu.). This outlet SOx represents a73% reduction in sulfur oxides emissions from the bituminous coal. Ifthis level of sulfur emissions is sufficient to meet environmentalregulations, the retrofit addition of reaction chamber(s) and reagentinjection system(s) is not necessary. In this case, the use of retrofitflue gas conversion technology for additional reductions of carbondioxide is possible, but not likely, due to lack of sufficient capacityin the existing particulate control device. That is, the original ashparticulate capacity less the required capacity for converted SOx (largeionic salts) may not leave sufficient capacity to make CO₂ control costeffective.

[0342] This example also illustrates significant reductions in pollutantemissions, based solely on fuel switching. The 16% lower fuel rate ofthe upgraded petroleum coke greatly contributes to lower environmentalemissions of ash particulates, sulfur oxides, and carbon dioxide. The97% reduction in ash particulates, noted above, was primarily due tolower fuel ash concentration. However, uncontrolled emissions of sulfuroxides and carbon dioxide are significantly reduced primarily due to the16% lower fuel rate. That is, the sulfur content of the upgradedpetroleum coke is 8% higher than the existing coal. Yet the upgradedpetroleum coke has 10% lower uncontrolled SOx. Similarly, the upgradedpetroleum coke has 5% higher carbon content (i.e. 87.5% vs. 83.3%). Yetthe uncontrolled emissions of carbon dioxide is reduced by 12% due tofuel switching.

Other Embodiments & Ramifications

[0343] Other embodiments of the present invention may presentalternative means to achieve at least some of the objectives of thepresent invention. Examples 2-5 are provided at the end of thisdiscussion to illustrate some of these embodiments of the presentinvention.

[0344] 1. Production of Premium Pet Coke: Modified Fluid Coking™ Process

[0345] Various operational changes in the Fluid Coking™ process canproduce a premium fuel-grade coke, in a manner similar to the delayedcoking discussion, above. Traditional Fluid Coking™ normally produces afuel-grade petroleum coke with higher metals and sulfur content thandelayed coke from the same feedstocks. Fluid coke, like shot coke, isspherical in shape (170 to 220 um), which makes it more difficult togrind. Its onion-like, laminated layers of coke cause a much higherdensity and hardness (HGI 30-40). As such, Fluid coke is even lessdesirable as a fuel, when compared to fuel-grade petroleum coke from thetraditional delayed coking process. Substantially less volatilecombustible material (4-8% VCM), much greater hardness, and much lowerporosity are three primary reasons. However, U.S. Pat. No. 4,358,290discusses the need to improve the combustion characteristics of fluidcoke. It discloses technology to increase the level of volatilecombustible material external to the coking process by blending thefluid coke with heavy petroleum liquid. For reasons discussedpreviously, leaving more VCM in the coke during the coking process canbe more desirable.

[0346] A. Traditional Fluid Coking™; Process Description

[0347]FIG. 4 provides a basic process flow diagram for a typical FluidCoking™ process. The Fluid Coking™ process equipment is essentially thesame, but the operation, as discussed below, is substantially different.Fluid Coking™ is a continuous coking process that uses fluidized solidsto further increase conversion of coking feedstocks to cracked liquids,and reduce volatile content of the product coke. Fluid Coking™ uses twomajor vessels, a reactor 158 and a burner 164.

[0348] In the reactor vessel 158, the coking feedstock blend 150 istypically introduced into the scrubber section 152, where it exchangesheat with the reactor overhead effluent vapors. Hydrocarbons that boilabove 975° F. are condensed and recycled to the reactor with the cokingfeedstock blend. Lighter overhead compounds 154 are sent to conventionalfractionation and light ends recovery (similar to the fractionationsection of the delayed coker). The feed and recycle mixture 156 issprayed into the reactor 158 onto a fluidized bed of hot, fine cokeparticles. The mixture vaporizes and cracks, forming a coke film (˜5 um)on the particle surfaces. Since the heat for the endothermic crackingreactions is supplied locally by these hot particles, this permits thecracking and coking reactions to be conducted at higher temperatures ofabout 510° C.-565° C. or (950° F.-1050° F.) and shorter contact times(15-30 seconds) versus delayed coking. As the coke film thickens, theparticles gain weight and sink to the bottom of the fluidized bed.High-pressure steam 159 is injected via attriters and break up thelarger coke particles to maintain an average coke particle size (100-600um), suitable for fluidization. The heavier coke continues through thestripping section 160, where it is stripped by additional fluidizingmedia 161 (typically steam). The stripped coke (or cold coke) 162 isthen circulated from the reactor 158 to the burner 164.

[0349] In the burner, roughly 15-25% of the coke is burned with air 166in order to provide the hot coke nuclei to contact the feed in thereactor vessel. This coke burn also satisfies the process heatrequirements without the need for an external fuel supply. The burnedcoke produces a low heating value (20-40 Btu/scf) flue gas 168, which isnormally burned in a CO Boiler or furnace. Part of the unburned coke (orhot coke) 170 is recirculated back to the reactor to begin the processall over again. A carrier media 172, such as steam, is injected totransport the hot coke to the reactor vessel. In some systems, seedparticles (e.g. ground product coke) must be added to these hot cokeparticles to maintain a particle size distribution that is suitable forfluidization. The remaining product coke 178 must be removed from thesystem to keep the solids inventory constant. It contains most of thefeedstock metals, and part of the sulfur and nitrogen. Coke is withdrawnfrom the burner and fed into the quench elutriator 174 where productcoke (larger coke particles) 178 are removed and cooled with water 176.A mixture 180 of steam, residual combustion gases, and entrained cokefines are recycled back to the burner.

[0350] B. Process Control of the Prior Art

[0351] In traditional Fluid Coking™, the optimal operating conditionshave evolved through the years, based on much experience and a betterunderstanding of the process. Operating conditions have normally beenset to maximize (or increase) the efficiency of feedstock conversion tocracked liquid products, including light and heavy coker gas oils. Thequality of the byproduct petroleum coke is a relatively minor concern.In “fuel-grade” coke operations, this optimal operation detrimentallyaffects the fuel characteristics of the coke, particularly VCM content,crystalline structure, and additional contaminants.

[0352] As with delayed coking, the target operating conditions in atraditional fluid coker depend on the composition of the cokerfeedstocks, other refinery operations, and the particular coker'sdesign. The desired coker products also depend greatly on the productspecifications required by other process operations in the particularrefinery. That is, downstream processing of the coker liquid productstypically upgrades them to transportation fuel components. The targetoperating conditions are normally established by linear programming (LP)models that optimize the particular refinery's operations. These LPmodels typically use empirical data generated by a series of coker pilotplant studies. In turn, each pilot plant study is designed to simulatethe particular coker design, and determine appropriate operatingconditions for a particular coker feedstock blend and particular productspecifications for the downstream processing requirements. The series ofpilot plant studies are typically designed to produce empirical data foroperating conditions with variations in feedstock blends and liquidproduct specification requirements. Consequently, the fluid cokerdesigns and target operating conditions vary significantly amongrefineries.

[0353] In normal fluid coker operations, various operational variablesare monitored and controlled to achieve the desired fluid cokeroperation. The primary operational variables that affect coke productquality in the fluid coker are the reactor temperature, reactorresidence time, and reactor pressure. The reactor temperature iscontrolled by regulating (1) the temperature and quantity of cokerecirculated from the burner to the reactor and (2) the feedtemperature, to a limited extent. The temperature of the recirculatedcoke fines is controlled by the burner temperature. In turn, the burnertemperature is controlled by the air rate to the burner. The reactorresidence time (i.e. for cracking and coking reactions) is essentiallythe holdup time of fluidized coke particles in the reactor. Thus, thereactor residence time is controlled by regulating the flow and levelsof fluidized coke particles in the reactor and burner. The reactorpressure normally floats on the gas compressor suction with commensuratepressure drop of the intermediate components. The burner pressure is setby the unit pressure balance required for proper coke circulation. It isnormally controlled at a fixed differential pressure relative to thereactor. The following target control ranges are normally maintained inthe fluid coker for these primary operating variables:

[0354] 1. Reactor temperatures in the range of about 950° F. to about1050° F.,

[0355] 2. Reactor residence time in the range of 15-30 seconds

[0356] 3. Reactor pressure in the range of about 0 psig to 100 psig:typically 0-5 psig,

[0357] 4. Burner Temperature: typically 100-200° F. above the reactortemperature

[0358] These traditional operating variables have primarily been used tocontrol the quality of the cracked liquids and various yields ofproducts, but not the respective quality of the byproduct petroleumcoke.

[0359] C. Process Control of the Present Invention

[0360] The primary improvements of the present invention aremodifications to the operating conditions of the Fluid Coking™ process,in a manner that is not suggested by prior art. In fact, these changesin operating conditions are contradictory to the teachings and currenttrends in the prior art. As noted previously, the operating conditionsof the prior art give first priority to maximizing cracked liquidproducts. The operating conditions of the present invention give firstpriority to consistently increasing the volatile combustible material inthe resulting petroleum coke to 13-50 wt. % VCM (preferably 15-30% VCM).Second priority is given to consistently provide a minimum-acceptablelevel of coke crystalline structure in the product coke. The thirdpriority is THEN given to maximize coker throughput and/or theconversion of coker feedstock blend to cracked liquid products. However,changing the VCM content and crystalline structure in fluid coke is muchmore challenging, relative to delayed coke. The operating conditionsrequired to achieve the objectives of the present invention weremoderate, yet specific changes relative to the prior art.

[0361] As discussed previously, fluid coker operating conditions varygreatly among refineries, due to various coker feedstocks, cokerdesigns, and other refinery operations. Therefore, specific operatingconditions (i.e. absolute values) for various refinery applications arenot possible for the present invention. However, specific changesrelative to existing operating conditions provide specific methods ofoperational change to achieve the desired objectives.

[0362] (1) Increased Volatile Combustible Material (VCM) in Fluid Coke:

[0363] In a manner similar to the delayed coking process, reduction inthe process operating temperature will cause an increase of volatilecombustible material in the resulting petroleum coke. That is, thereduction in process (or reactor) temperature will reduce the crackingand coking reactions, and thereby, leaving more unreacted cokerfeedstock and cracked liquids in the coke as volatile combustiblematerial. However, the different mechanism of coking in the FluidCoking™ process may require a more significant reduction in temperatureto achieve the same level of VCM in the petroleum coke. In the FluidCoking™ process, the temperature of the fluidized coke particles leavingthe coke burner would be the primary temperature to reduce. Decreasingthis temperature by 10-200° F. (preferably 10-80° F.) can increase thefluid coke VCM to the preferable range of 15-30%. Reduction of feedtemperature and the operating temperature of the reactor would also playsecondary roles in increasing the VCM on the petroleum coke. However, ifthe reactor temperature is too low, the fluid coker will bog down andlose fluidization. If the reactor temperature (in a particular fluidcoker) approaches this bogging condition prior to achieving the desiredVCM increase, other operational parameters can be modified to achievedthe desired VCM. The reduction of coke stripping and the addition ofoily sludges/substances or hazardous wastes in the final quench of theproduct coke can provide the additional VCM required.

[0364] The reduction of coke stripping at the base of the fluid cokerreactor can also increase the product coke VCM. The reduced efficiencyof the stripping section will leave more VCM on the cold coke circulatedto the burner. In the burner, less coke (i.e. higher VCM coke) would beburned to provide the same heat requirements. Consequently, a greateryield of higher VCM product coke would be produced.

[0365] The addition of oily sludges (or other oily substances) orhazardous wastes in the final quench of the product coke can alsoprovide the additional VCM required. Similar to the delayed-coke drumquenching process, the quenching of product (fluid) coke in the quenchelutriator can be used to achieve the desirable VCM content. That is,oily sludges or other oily substances, such as used lubricating oils,can be added to the quench water to leave more VCM on the fluid cokeproduct. Various types of hazardous wastes can be used as a raw material(vs. waste) in this modified process, instead of underground injectionor less desirable disposal methods. However, environmental regulationsmay require a delisting process or other means of dealing with thehazardous waste requirements. This method can be effective in evenlydistributing quench material throughout the coke, and provide variousoptions regarding the quality of VCM content. This option is discussedfurther in other embodiments.

[0366] (2) Acceptable Fluid Coke Crystalline Structure:

[0367] Unfortunately, operational changes in the fluid coker will notsignificantly impact the crystalline structure of the product fluidcoke. The fluid coke has onion-like, laminated layers of coke due to thenature of the Fluid Coking™ process. As such, the product fluid coke hasthe consistency of coarse sand (vs. sponge) with a much higher densityand much lower porosity. Consequently, the high VCM coke can havelimited utility and can be limited to applications where the currentcrystalline structure is acceptable. Also, this denser crystallinestructure may require higher VCM quality and quantity versus spongecoke.

[0368] D. Low-Level Decontamination of Coker Feedstocks:

[0369] Desalting Operations

[0370] As in the exemplary embodiment, the three-stage desaltingoperation will provide the simplest and best known approach to providethe low-level decontamination of the product fluid coke required forcombustion applications. The low-level decontamination of the feedstockswill have similar effects in the fluid coker. The three-stage desaltingoperation will minimize (or substantially reduce) the sodium content ofthe fluid coke. This sodium reduction is expected to be sufficient toprevent the formation of undesirable sodium compounds in the combustionprocess. However, the reduction of vanadium and other metals may not beas effective. The Fluid Coking™ process tends to concentrate more ofthese materials in the product fluid coke.

[0371] 2. Production of Premium “Fuel-Grade” Pet Coke: AdditionalEmbodiments

[0372] Additional embodiments of the various means to produce a premium“fuel-grade” petroleum coke are described below. Any, all, or anycombination of the embodiments, described above or below, can be used toachieve the objects of this invention. In any combination of theembodiments, the degree required may be less than specified here due tothe combined effects.

[0373] A. Control of VCM in the Petroleum Coke; Additional Embodiments

[0374] (1) Delayed Coking; Other Process Variables:

[0375] In the delayed coking process, other process parameters couldalso be modified to achieve the desired level of VCM on the petroleumcoke. That is, operational control variables other than feed heateroutlet temperatures may be modified to achieve the major objectives ofthe present invention and/or more optimal operation for a particularrefinery. These other operational control variables may include, butshould not be limited to, the coker feedstock blend, drum pressure, hattemperature, cycle time, recycle rate, and feed rate. Modifications tothese operational variables may or may not accompany a decrease in thefeed heater outlet temperature. Process variables that increase thethermal coking mechanism (such as feedstock modifications) would bepreferable; increasing sponge coke as well as VCM. Coker feedstockpretreatment (e.g. hydrotreating) has also been noted to increase cokeVCM, in certain situations. In addition, this embodiment anticipates (1)various combinations of process variable modifications and (2) differentcontrol priorities (for meeting various product specifications) thatalso achieve the major objectives and basic intent of the currentinvention.

[0376] (2) Fluid Coking™; Other Process Variables:

[0377] In a similar manner, other process parameters of the FluidCoking™ process could also be modified to achieve the desired level ofVCM on the petroleum coke. Operational control variables, other thanFluid Coking™ reactor temperature, may be modified to achieve the sameobject for more optimal operation for a particular refinery. These otheroperational control variables may include, but should not be limited to,the coker feedstock blend, feed rate, reactor pressure, reactorresidence time, and recirculated coke particle size. Coker feedstockpretreatment (e.g. hydrotreating) can increase coke VCM, in certainsituations. Modifications to these operational variables may or may notaccompany a decrease in reactor temperature, recirculated coke finestemperature and/or feed temperature. In addition, this embodimentanticipates (1) various combinations of process variable modificationsand (2) different control priorities (for meeting various productspecifications) that also achieve the major objectives and basic intentof the current invention.

[0378] (3) Flexicoking™, Changes in Process Variables:

[0379] A case could be made for increasing the VCM and/or improvingcrystalline structure of the purge coke in Flexicokin Process changeswould be similar to the process changes made in Fluid Coking™, due totheir similar design basis. However, the additional coke devolatilizingin the Flexicoking™ process make the increased VCM more difficult.Furthermore, higher VCM coke would not likely have substantial utility,since Flexicoking™ consumes most of its coke internally in its gasifier.

[0380] (4) Reduced Stripping of Product Coke:

[0381] In another embodiment, less stripping of the product coke mayprovide part (or all) of the desired increase in the volatilecombustible material in the petroleum coke. Reducing the steaming of theproduct coke will significantly decrease the liquid hydrocarbons removedfrom the coke, via vaporization and/or entrainment. Thus, the VCMcontent of the product coke is increased. Most of the VCM increase isexpected to be cracked liquids with boiling temperatures <1000° F. Thiscan effectively improve the quality as well as the quantity of VCM onthe petroleum coke. This embodiment can be applicable to the cokestripping in delayed coking, Fluid Coking™, Flexicoking™, and othertypes of coking processes, available now or in the future. In delayedcoking, an added benefit is the potential for a significant reduction inthe decoking cycle. The elimination of the initial steam-cooling step inthe decoking procedure could help decrease decoking cycle time by up to3 hours.

[0382] (5) Injection of Oily Sludges/Fluids in Coke Quench:

[0383] In another embodiment, various oily sludges or other fluidscontaining hydrocarbon substances (e.g. used lubricating oils) can beused in the quench for the product coke to increase its VCM. The methodof introducing the oily sludges/fluids may be similar to that describedin U.S. Pat. No. 3,917,564 (Meyers; 11/4/1975). However, the injectionof hydrocarbons in the quench may continue until the coke temperaturereached 250-300° F. (vs. 450° F.). This modified method would allow highquality VCMs (boiling ranges of 250-850° F. and heating values of16-20,000 Btu/lb) to be evenly dispersed on the upgraded petroleum coke.Another improvement may also include the introduction of the oilysludges/fluids without the two initial steam cooling steps, to reducedecoking cycle time and leave more VCM on the petroleum coke. A furtherimprovement would result from segregating the hydrocarbon substances byboiling ranges and inject them with the quench at the appropriatecooling stage to vaporize the water carrier, but not the hydrocarbonfluids. That is, an exemplary method may inject the water quench(without initial steam cooling) in stages that maintains coketemperatures below the boiling ranges of the segregated hydrocarbonsubstances it contains. In addition, the injection of the quench in thetop of the drum (or other locations) may provide further advantage tocondense escaping VCM vapors that are entrained in the steam orvaporized by localized hot spots in the coke drum. The optimization ofthese methods for particular refineries would maximize (or substantiallyincrease) retention of these oily substances integrated in the upgradedpetroleum coke.

[0384] Most of the VCM increase is expected to come from unreactedhydrocarbons. The degree of VCM from 1000° F.+ materials will depend onthe type of sludges or oily substances. If oily substances are chosen toproduce VCM <850° F., this embodiment can improve the quality as well asthe quantity of the VCM. In addition, the resulting fuel-grade petroleumcoke is expected to be less sensitive to the disposal of various sludgesand oily substances, when compared to similar disposal methods for othergrades of petroleum coke. However, certain sludges can add significantash content and undesirable contaminants, such as sodium, to the productcoke. This embodiment can be applicable to the coke quenching in delayedcoking, Fluid Cokin™,Flexicoking™ and other coking processes, availablenow or in the future.

[0385] (6) Injection of Oily Sludges/Fluids in Coking Process:

[0386] In another embodiment, various oily sludges or other fluidscontaining oily substances (e.g. used lubricating oils) can beintroduced into other parts of the coking process (e.g. cokerfeedstocks) to increase the product coke VCM. The method of introducingthe oily sludges/fluids may be similar to that described in U.S. Pat.No. 4,666,585 (Figgins & Grove; May 19, 1987). However, the oily sludgesin this application would be segregated to give first priority to oilysludges that are predominantly hydrocarbons with boiling rangesexceeding 600-700° F. The introduction points in the delayed cokingprocess should include, but not be limited to coker feedstock,fractionator, coke drum, and other streams prior to coking. Similarly,introduction points in the Fluid Coking process should include, but notbe limited to, coker feedstock, feed heater, scrubber section, cokerreactor, and other streams prior to coking.

[0387] Similar to coker feedstocks, the VCM increase is expected to comefrom unreacted materials and cracked liquids. The degree of VCM from1000° F.+ materials will again depend on the type of sludges or oilysubstances. As above, the resulting fuel-grade petroleum coke isexpected be less sensitive to the disposal of various sludges and usedlubricating oil, when compared to similar disposal methods for othergrades of petroleum coke. Similarly, certain sludges can add significantash content and undesirable contaminants, such as sodium, to the productcoke. This embodiment can be applicable to delayed coking, FluidCoking™, Flexicoking™ and other coking processes, available now or inthe future.

[0388] (7) Injection Oo Hazardous Wastes in Coking Process or CokeQuench:

[0389] Various types of hazardous wastes can be injected as a rawmaterial or chemical feedstock (vs. waste) in this modified process.Selective use of hazardous wastes with desirable volatilization andcombustion properties (e.g. predominantly hydrocarbons) can greatlyimprove the quality of the upgraded petroleum coke's VCM. At the sametime, the hazardous wastes could be effectively used in this product,instead of underground injection or less desirable disposal methods. Insome cases, the EPA delisting or other process may be required toaddress environmental regulations regarding hazardous wastes. In manycases, the concentration of the hazardous waste in the resulting cokewould be sufficiently low to minimize (or greatly reduce) hazardouswaste characteristics.

[0390] The addition of hazardous wastes in the coking reaction (viablending with coker feedstock or other injection points) can provide acost-effective source of VCM for the resultant coke with limitedreductions in cracked liquid production. The method of introducing thehazardous wastes in the delayed coking cycle may be similar to thatdescribed in U.S. Pat. No. 4,666,585 (Figgins & Grove; May, 19, 1987).However, the hazardous wastes in this application may be segregated togive first priority to oily sludges that are predominantly hydrocarbonswith boiling ranges exceeding 600-700° F. The introduction points in thedelayed coking process should include, but not be limited to cokerfeedstock, fractionator, coke drum, and other streams prior to coking.Similarly, introduction points in the Fluid Coking process shouldinclude, but not be limited to, coker feedstock, feed heater, scrubbersection, coker reactor, and other streams prior to coking.

[0391] Injection in the coke quench, however, may be preferable toincrease the quantity of VCM with low boiling points (i.e. 250-850° F.),remaining with the coke (vs. overhead product as cracked liquid).Consequently, this higher quality VCM would enhance the ignition andcombustion characteristics of the upgraded coke. Injection via cokequench can be effective in evenly distributing quench materialthroughout the coke. The method of introducing the hazardous wastes inthe coke quench may be similar to that described in U.S. Pat. No.3,917,564 (Meyers; Nov. 4, 1975). However, the injection of hazardouswastes in the quench would continue until the coke temperature reached250-300° F. (vs. 450° F.). This modified method would allow high qualityVCMs (boiling ranges of 250-850° F. and heating values of 16-20,000Btu/lb) to be evenly dispersed on the upgraded petroleum coke. Anotherimprovement may also include the introduction of the hazardous wasteswithout the two initial steam cooling steps, to reduce decoking cycletime and leave more VCM on the petroleum coke. A further improvementwould result from segregating the hydrocarbon substances by boilingranges and inject them with the quench at the appropriate cooling stageto vaporize the water carrier, but not the hydrocarbon fluids. That is,an exemplary method may inject the water quench (without initial steamcooling) in stages that maintains coke temperatures below the boilingranges of the segregated hydrocarbon substances it contains. Inaddition, the injection of the quench in the top of the drum (or otherlocations) may provide further advantage to condense escaping VCM vaporsthat are entrained in the steam or vaporized by localized hot spots inthe coke drum. The optimization of these methods for particularrefineries would maximize (or substantially increase) retention of theseoily substances integrated in the upgraded petroleum coke. Similarresults are expected for many types of hazardous wastes.

[0392] (8) Combination of Embodiments to Achieve Desirable BurningProfile:

[0393] As noted previously, the end-users' VCM specification can belowered by providing the optimal burning profile for his combustionsystem design. That is, the VCM increase can preferably be a combinationof hydrocarbons with various boiling ranges. To a certain extent, theburning profile of the petroleum coke can be adjusted by a combinationof the above embodiments. For example, most of the VCM increase can comefrom a decrease in heater outlet temperature and the addition of usedlubricating oils to the coker feed, with most VCM >1000° F. materials.The remainder of the VCM could come from reduced steaming and using oilysludges in the quench, producing VCM with lower boiling ranges (e.g.350-1000° F.). These lower boiling range VCM would improve flameinitiation, stability, and intensity. Consequently, the types ofvolatile combustible materials could be varied to a reasonable degree,based on pilot studies for production and burning of petroleum coke. Inthis and similar approaches, the formulation of petroleum coke can becustom-made to match (to the extent possible and reasonable) the burningprofile of the end-user's combustion system. In this manner, theend-user can optimize the operation of his combustion system withoutexpensive design modifications to accommodate the fuel switch topetroleum coke. Consequently, this approach is conducive to achievingthe lowest VCM required by the end-user's current combustion system.

[0394] (9) Genral Issues for Various Embodiments of VCM Control:

[0395] As noted above, the use of less stripping and/or quenchcontaining hydrocarbons can eliminate or reduce the need for additionalVCM from the coker feedstock. However, the petroleum coke VCM must beable to endure the weathering (rain, snow, etc.) in transport andstorage, and provide the VCM required by the end-user at its facility.That is, VCM from lighter hydrocarbons may be lost from the productcoke, due to higher solubility and continual washing.

[0396] After the specific level and types of VCM required are determinedfor any given product coke, engineering factors will determine theoptimal use for any of the above embodiments, separately or incombination, for a particular refinery. In any combination of theembodiments, the degree required may be less than specified here due tothe combined effects. Finally, these concepts and embodiments may beapplied to other types of coking processes, available now or in thefuture.

[0397] As noted previously, the main objective of the present inventionis to achieve a petroleum coke with acceptable VCM, crystallinestructure, and decontamination levels, preferably specified by theend-user. THEN, the conversion of coker feedstock blend to lighterliquid products is maximized. Optimization of all operating conditionsand economic constraints via refinery LP computer models is anticipated.However, this model would likely include a petroleum coke product havingthe end-user specified VCM, crystalline structure, and decontaminationlevels as operational constraints.

[0398] B. Control of Petroleum Coke Crystalline Structure; AdditionalEmbodiments

[0399] (1) Other Coker Operating Variables:

[0400] In coking processes, other process parameters could also bemodified to achieve the desired level of crystalline structure withinthe petroleum coke. Operational control variables other than drum andcoke recirculation temperatures may be modified to achieve the sameobject or more optimal operation for a particular refinery. These otheroperational control variables would preferably increase the thermalcoking mechanism and/or decrease the asphaltic coking mechanism to bringR-values down to an acceptable level. For delayed cokers, these otheroperational control variables may include, but not be limited to, thecoker feedstock blend, fractionator pressure, hat temperature, cycletime, and feed rate. For Fluid Coking™, these other operational controlvariables may include, but not be limited to, the coker feedstock blend,solids circulation rate, fractionator pressure, and feed rate.Modifications to these operational variables may or may not accompany adecrease in the outlet temperatures of the respective feed heaters orother operating temperatures. Process variables that increase VCM whiledecreasing shot coke would be preferable.

[0401] (2) Coker Feedstock Modifications:

[0402] Coker feedstocks could also be modified to achieve the desiredlevel of crystalline structure within the petroleum coke. That is,feedstock modifications can achieve the same object or more optimaloperation for a particular refinery. These would preferably increase thethermal coking mechanism and/or decrease the asphaltic coking mechanismto bring R-values down to an acceptable level. Coker feedstockmodifications could include, but not be limited to (1) dilution withfluids/feedstocks with less asphaltene and resins content, (2) theaddition of highly aromatic feedstocks, such as FCCU slurry oil, and/or(3) coker feed pretreatment (e.g. hydrotreating or otherdesulfurization). This embodiment can be applicable to delayed coking,Fluid Coking™, Flexicoking™ and other coking processes, available now orin the future.

[0403] (3) Coker Additives:

[0404] Various chemical and/or biological agents could be added to thecoking process to further help inhibit the formation of shot coke and/orpromote the formation of desirable sponge coke. One such additive mayinhibit the role certain contaminant particles play in the formation ofshot coke. Also, U.S. Pat. No. 4,096,097 (Yan: Jun. 20, 1978) describesa method for inhibiting shot coke and promoting sponge coke formationfor the production of an electrode grade petroleum coke having desiredgrindability qualities. This method comprises adding an effective amountof oxygen-containing, carbonaceous material (which tends to decompose athigh temperatures) to the delayed coker and/or recycle/feed. Theaddition of oxygen-containing carbonaceous material, in combination withother features of the present invention, may further help eliminate orsubstantially reduce shot coke formation and promote sponge cokecrystalline structure. Examples of the oxygen-containing carbonaceousmaterial include, but are not limited to, sawdust, newspaper, alfalfa,wheat pulp, wood chips, wood fibers, wood particles, ground wood, woodflour, wood flakes, wood veneers, wood laminates, paper, cardboard,straw, cofton, rice hulls, coconut shells, peanut shells, plant fibers,bamboo fibers, palm fibers, kenaf, bagasse, sugar beet waste, coal(e.g., subbituminous coal), lignite, other cellulosic materials andwastes, other oxygen-containing carbonaceous materials, and othermaterials having similar characteristics. The carbonaceous materialpreferably has an oxygen content in the range of from about 5% to about60% by weight. However, it should be recognized that carbonaceousmaterials having an oxygen content outside of this range may also beused in the present invention.

[0405] The inventor has also made the surprising discovery that theaddition of other chemical agents, with or without an oxygen content inthe range of from about 5 to about 60 wt. %, can further promote theproduction of sponge coke and eliminate or substantially reduce shotcoke formation. While not wanting to be bound by any particular theoryof operability, these other chemical agents tend to increase porosity byproducing lighter gases (i.e., Molecular Weight <50) that rise throughthe coking mass in the petroleum coking process. This theory ofoperability is similar to foaming agents for plastics, such aspolystyrene, and to the method of adding oxygen-containing carbonaceousmaterials to the delayed coker and/or recycle/feed. The production ofthese lighter gases can be caused by various mechanisms. Thesemechanisms include, but are not limited to, (1) the decomposition of thechemical agents at petroleum coking process conditions (e.g., thermalcracking) and (2) other chemical reactions in the coking process.

[0406] It should, however, be recognized that the current invention isnot limited to adding carbonaceous chemicals and/or chemicals thatcontain about 5 to about 60% oxygen by weight. As noted above, thecarbonaceous material and/or chemicals may have an oxygen contentoutside of this range and still promote the production of sponge cokeand eliminate or substantially reduce shot coke formation. Furthermore,the lighter gases are not limited to those containing oxygen (e.g., CO₂,H₂O, etc.). In fact, for reasons described below, the preferred lightergases released by the decomposition of the chemical agents may behydrogen, methane, propane, and other light hydrocarbons. Finally, thechemical agents do not necessarily have to be carbonaceous materials.That is, the chemical agents do not have to contain carbon (i.e.,organic) as long as they meet certain criteria in their decomposition atthe coking process conditions.

[0407] The chemical agents of the current invention may have unique andimproved features over the oxygen-containing, carbonaceous materials.The exemplary chemical agents may have some or all the followingcharacteristics:

[0408] 1. Release (1) hydrogen, (2) light hydrocarbons (C₃—), (3) otherlight gases without oxygen, and/or (4) light gases with oxygen upondecomposition in the coking process conditions

[0409] a. Promote high-porosity sponge coke (vs. shot coke): Increaseporosity, improve carbon adsorption character, and improve grindabilityproperties; Proposed mechanisms include, but are not limited to:

[0410] 1. The light gases, under pressure, pass through the coke masscreating voids in the developing petroleum coke crystalline structure:The petroleum coke pore size is partially related to the gas molecules'sizes. That is, smaller gas molecules lead to smaller pore sizes. Thus,preferable adsorption character can be effected by control of gasmolecular size.

[0411] 2. Disturb crystal growth and prevent undesired coke formation,particularly shot coke

[0412] 3. Limit petroleum coke crystal size due to nuclei of certainagents, coupled with the proper aromatic-asphaltic ratio established vialower drum temperatures

[0413] b. Quench the cracking/coking reactions via hydrogen reactionwith free radicals to break these endothermic, chain reactions: preventsvapor overcracking and improves coker products, as well as decreases thecoke yield and improves coke quality (see 1a: 2 & 3)

[0414] c. Provide higher value coker off gas products: Hydrogen andlight hydrocarbons (versus oxygen-containing gases such as CO₂, H₂O,etc.) pass through the coke and are used further

[0415] 2. Tend to form valuable liquid hydrocarbon products fromdecomposition in the coking process conditions: vs. greater than 50%coke yields of oxygen-containing carbonaceous materials (wood, lignite,waste coals, etc.)

[0416] 3. Inexpensive & readily available in refinery area (e.g.,recycled or waste materials)

[0417] Examples of the chemical agents include, but are not be limitedto, various types of plastics, rubber, cardboard, and paper. Recycle orwaste streams may be used. The chemical agent preferably has a particlesize less than 100 mesh, and more preferably less than 50 mesh. However,it should be recognized that the chemical agent may have any particlesize that enables it to provide desirable results. Alternatively, thechemical agent can be injected into the coking process in forms otherthan fine particulates. For example, the injected chemical agents can beliquid (e.g., melted plastics) and/or more than one phase (e.g., a2-phase slurry). In addition, the chemical agent preferably does nothave any inherent impurities that detract from the intended use of theend coke product.

[0418] Various types of plastics can often meet most, if not all, of theabove criteria for the exemplary chemical agents in the currentinvention. For example, plastics or chemicals that may be used in thepresent invention include, but are not limited to, high densitypolyethylene (HDPE), low density polyethylene (LDPE), polypropylene,polystyrene, polyvinyl chloride (PVC), polyvinyl acetate,polyacrylonitrile, polyurethane, acrylonitrile butadiene styrene (ABS),various copolymers, and other plastics and chemicals having suitablecharacteristics. In this regard, it should be recognized that mostplastics decompose at the coker operating conditions and release lightergases (molecular weight less than 50) as well as more valuable liquidhydrocarbons (C₄₊ with boiling points less than 850° F.). Depending onthe specific plastic compounds, lighter gases would include, but are notlimited to, hydrogen, methane, ethane, propane, ammonia, water, carbondioxide, and carbon monoxide. The ability to use mixed plastics in thecurrent invention provides a major advantage for recycling plastics.That is, the current barrier to recycling plastics (separating plasticsby type) is effectively overcome. In addition, readily accessiblehydrogen generated from certain plastics can be effectively used toquench excessive cracking and coking reactions in the coke mass and thevapor phase of the cracking products. That is, optimal amounts ofhydrogen can be maintained to prevent (1) ‘vapor overcracking’ (i.e.,excessive thermal cracking in the vapor phase) that yields lower valueproducts, and (2) excessive coking of the desired ‘cracked liquids’ thatyields additional petroleum coke of lower value (vs. ‘cracked liquids’).The sources of the quench hydrogen include, but are not limited to,hydrogen gas, methane, ethane, propane, ammonia, water, and/or otherchemical agent derivatives that have readily accessible hydrogen atoms.The quantity and quality of the hydrogen and other light gases generatedfrom the plastics depends on (1) the types and quantities of variousplastics, and (2) the design and operation of the petroleum cokingprocess.

[0419] The optimal amount(s) and point(s) of injection for the chemicalagent(s) of the current invention may vary with coker feedstocks andcoker operating conditions. The amount of light gases (molecular weight<50) and accessible hydrogen generated by the decomposition of thechemical agent(s) is key to (1) improved petroleum coke crystallinestructure and (2) the desired quenching of the excessive cracking andcoking reactions. The accessible hydrogen is primarily, but not totally,responsible for the desirable quenching of excessive cracking and cokingreactions. That is, the other light gases, the coke drum temperaturedecrease, and other operational changes of the current invention havequench effects, as well. While not wanting to be bound by any particulartheory of operability, the quench hydrogen is expected to satisfy theelectron structure sought by the free-radical chemical species, that arecritical to these endothermic, chain reactions. Eliminating therecurring, free-radical compounds typically stops or quenches thecracking and coking reactions. Quenching the excessive coking reactionsis one mechanism that disturbs coke crystal growth; limiting crystalsize, increasing coke porosity, and decreasing coke yields. Thus, vaporovercracking and excessive coking can be effectively reduced. However,the point of the light gases' release in the coking process is alsoimportant to prevent premature quenching of the coking and crackingreactions. This premature quenching of cracking and coking reactions canessentially defeat the primary purpose of the coking unit: crack heavyhydrocarbon compounds into more usable and valuable hydrocarbonsreferred to as ‘cracked liquids.’ Thus, the optimal quantity, quality,and point of injection for the chemical agents of the current inventionneed to be determined (e.g., pilot plant studies) for each set of cokerfeedstocks and associated operating conditions. In general, the quantityof carbonaceous material(s) and/or chemical agent(s) may be about 0.5 toabout 20 weight percent, and more preferably about 0.5 to 10 weightpercent, of the feed. Standard engineering principles and practices canbe employed by one skilled in the art to determine the optimal quantity,quality, and point(s) of injection for the appropriate chemical agent(s)of the current invention.

[0420] In light of the above considerations, the carbonaceousmaterial(s) and/or the chemical agent(s) are preferably introduced intothe feedstream in a delayed coking process prior to the coker heaterand/or between the coker heater and the coking drums. For the samereasons, in a Fluid Coking™ process, the carbonaceous material(s) and/orthe chemical agent(s) are preferably introduced into the feedstreamprior to the feed heater and/or between the coker heater and the burner.As noted, there may be multiple points of injection. It should also berecognized that some of the carbonaceous material(s) and/or the chemicalagent(s) can be injected into the feedstream entering the fractionatorin a delayed coking process or entering the reactor in a Fluid Coking™process depending on the coker feedstock and the coker operatingconditions. Moreover, it should be recognized that the carbonaceousmaterial(s) and/or the chemical agent(s) can be introduced at otherpoints in the thermal cracking process depending on the coker feedstockand the coker operating conditions.

[0421] (4) Current Refinery Operation:

[0422] In some situations, the end-users combustion system is capable ofhandling the coke crystalline structure produced by the coker withoutadditional modifications. For example, process modifications to achievethe higher VCM coke produce acceptable levels of shot coke (or cokecrystalline structure) without further process modifications.Alternatively, refineries may have coker feedstocks (e.g. lighter crudeblends) with sufficiently low asphaltenes and resins, that theproduction of sponge coke is already prevalent. In these cases, anincrease in coke VCM in the coking process normally increases the cokeporosity. As such, an increase in coke VCM alone can be sufficient toachieve an upgraded coke capable of self-combustion.

[0423] (5) General Issues for Control of Coke Crystalline Structure:

[0424] After the specific levels and types of crystalline structurerequired is determined for any given product coke, engineering factorswill determine the optimal use for any of the above embodiments,separately or in combination. In any combination of the embodiments, thedegree required may be less than specified here due to the combinedeffects. Again, these concepts and embodiments may be applied to delayedcoking, Fluid Coking™, Flexicoking™ and other types of coking processes,available now or in the future.

[0425] C. Decontamination of Petroleum Coke; Additional Embodiments

[0426] (1) Current Desalting Process with Improved Efficiency:

[0427] The conventional refinery desalting processes, currently in therefinery, can be modified to achieve the low-level decontaminationrequired. One or two stage desalter systems can be improved to >95+%efficiency with sodium levels <5 ppm in the crude or vacuum distillationfeedstock. In some cases, this level of decontamination can besufficient.

[0428] (2) Other High-Efficiency Desalting Operations:

[0429] Filtration, catalytic, and other types of hydrocarbon desaltingoperations are in various stages of development. The present inventionanticipates the integration of these new types of desalting operations.These other desalting technologies can provide sufficientdecontamination, if a sodium specification of <15 ppm (preferably <5ppm) in the coker feedstock is achieved.

[0430] (3) Coke Treatment within the Coking Process:

[0431] An additional embodiment for low-level decontamination of thepetroleum coke can include coke treatment in the coking process. In thedecoking cycle of the delayed coking process, the petroleum coke goesthrough steam stripping and quenching phases. During these phases, traceamounts of acid, caustic or other chemical additives could be added tothe water to promote further reduction of contaminants. In a mannersimilar to the desalting process, the “water-washing” of the petroleumcoke with steam and water would remove water-soluble compounds. Thedecrease in decoking cycle (created by the reduced drilling time of thesofter coke) could be used for additional residence or treating time, ifappropriate. A closed-loop water system with independent water treatmentmay also be desirable for this embodiment. In addition, the introductionof biological treatment of the petroleum coke can be included in thisembodiment. Overall, this embodiment may be more desirable than enhancedcrude oil desalting systems, due to the thermal decomposition of thecoking process. That is, many of the complex organic structurescontaining the contaminants have been cracked, potentially exposing thecontaminants for further treatment (e.g. reaction and entrainment). Thecombination of both embodiments may be very cost-effective. Similarly,the quench phase (and possibly the stripping phase) of the Fluid Coking™process can also provide an opportunity for this embodiment of low-leveldecontamination.

[0432] (4) Coke Treatment After Coking Process:

[0433] Another embodiment of the present invention can providedecontamination of the petroleum coke after the coking process iscomplete. As noted above, many of the complex organic structurescontaining the contaminants have been cracked, in the coking process,potentially exposing the contaminants for further treatment. After thedegree of required decontamination and the properties of the upgradedcoke are known, normal engineering skills would be sufficient to developvarious engineered solutions to treat the coke after the coking process.Options for this embodiment might include various physical, chemical,and/or biological treatments. Another option may also use thetransportation and storage of the coke to increase treatment time. Thisoption may require final treatment steps, rinsing, and water treatmentsystems at the coke user's facility.

[0434] (5) Coker Feedstock Dilution:

[0435] Another embodiment of the present invention would modify thecoker feedstocks to reduce the concentration of contaminants in thefinal coke product. Coke-producing feedstocks with lower concentrationsof the contaminants of concern would be added to the coker feed todilute the concentration of contaminants in the petroleum coke product.

[0436] (6) Coker Feedstock Pretreatment:

[0437] Yet another embodiment of the present invention may include othertypes of coker feedstock pretreatment. From a technical perspective, theaddition of a coker feed pretreatment system would likely be the mosteffective means of addressing the detrimental impacts of petroleum cokecontaminants. However, this embodiment often is not economicallyoptimal. The optimal coker feed treatment system would depend on thecomposition of the coker feedstocks and the needs of the petroleum cokeuser. After the degree of required decontamination and the impacts offeed treatment decontamination are known, various engineered solutionswould be available to treat the coker feedstocks. This coker feedtreatment system may or may not include more sophisticateddemetallization and/or desulfurization technologies, described in theprior art. For example, hydrotreating or hydrodesulfurization of thecoker feedstocks can decrease the sulfur content by 80-95%. If most ofthe sulfur is removed from the product coke in this manner, the excesscapacity of in a utility boiler's existing particulate control devicecan be used for the collection of other gases (e.g. carbon dioxide) thatare converted to collectible particulates. Also, desulfurization of thecoker feedstock may provide further advantage by increasing coke VCM andpromoting sponge coke.

[0438] (7) Current Refinery Operation with no Further Decontamination:

[0439] Another embodiment of the present invention may include notreatment of any kind for decontamination of the coke. As notedpreviously, the effects of petroleum coke's high metals content incombustion and heat transfer equipment is not well understood ordefined. The design and operation of the user's combustion system playsa major role in determining whether the current level of contaminants inthe coke is acceptable or not. Therefore, some oil refineries, dependingon the coker feedstock blend and coker operation, may be able to providethe upgraded petroleum coke without further coke decontamination.

[0440] (8) General Issues for Embodiments of Low-Level Decontamination:

[0441] After the specific level of required coke decontamination isdetermined for any given product coke, engineering will determine theoptimal use for any of the above embodiments, separately or incombination. The combination of any of these embodiments may reduce thelevel of decontamination required by each embodiment, individually.Finally, these concepts and embodiments may be applied to other types ofcoking and desalting processes, available now or in the future.

[0442] 3. Further Optimization of Delayed Coking Process

[0443] It has been further discovered that the preceding processmodifications may be a subset of process modifications to optimize cokercracking and coking reactions. This discovery, an enhanced theory ofoperation, provides further insight into process mechanisms and chemicalreactions of potential coker process modifications. As such, the cokerprocess modifications, described previously, are discussed in adifferent light for clarification. In addition, coker processmodifications are further discussed. These additional embodiments ofcoker process modifications are the primary focus of this section.However, previous embodiments of potential coker process modificationsshould not be limited by this discovery and its enhanced theory ofoperation.

[0444] A. Coker Process Modifications: Optimization of Cracking & CokingReactions

[0445] This discovery has led to the optimization of coking and crackingreactions in both the liquid and vapor phases of the coking process. Inthe past, the coking process has been viewed as a complex mass ofphysical changes and various competing chemical reactions, primarilycoking and cracking reactions. As described previously, the cokingprocess has two major coking mechanisms: thermal coking and asphalticcoking. Thermal coking comprises endothermic chemical reactions:primarily condensation and polymerization of polycyclic aromatichydrocarbons (PAHs). Asphaltic coking is an adiabatic physical change:essentially desolutation of asphaltenes and resins. The predominantcracking mechanism is noted to be free-radical, dehydrogenation. Thisendothermic, cracking reaction has several process steps. The initialsteps involve the generation of free-radicals that seek electrons tostabilize their electron configurations and initiate cracking or thecleavage of chemical bonds, particularly carbon-to-carbon bonds. Thecoker operating conditions and chemical components of the cokerfeedstocks play major roles in determining which reactions are morefavorable.

[0446] Traditionally, the coker feedstocks are heated to the highestpractical temperature to maximize reactivity and drive the endothermiccracking and coking reactions to completion. In general, this approachhas been viewed as the most expedient and efficient manner to achievethe primary objective for traditional delayed cokers: maximize theextraction of valuable cracked liquids from the heavy, coker feedstocks.In this manner, many cokers treat the residual petroleum coke as aby-product with little to no value. However, excessive cracking andcoking reactions in the liquid and vapor phases can be suboptimal.Consequently, certain process mechanisms and operating conditions havebeen developed to favor desirable reactions over less desirablereactions. In this manner, the coker reactions are optimized.

[0447] In the liquid phase, the cracking reactions may generally bepreferred over the coking reactions. In traditional coking processes,cracking the heavy hydrocarbon feedstocks into more valuable, lighthydrocarbons is strongly preferable to any reactions that producepetroleum coke. However, it has been further discovered that certainheavy hydrocarbons in the coker feedstocks can be preferably left withthe coke (vs. in the heavy coker gas oils or coker recycle). That is, asmall fraction of the heavy hydrocarbons that traditionally ends up inthe heavy coker gas oil can offer more value in improving the pet cokequality versus decreasing the coker gas oil qualities.

[0448] The primary coker feed components of concern are usually veryheavy, polycyclic aromatic hydrocarbons (PAHs) that contain undesirablesulfur and metals. These heavy, polycyclic aromatic hydrocarbons aretypically vapors in the coke drum between 770° F. and 925° F, usually800-850° F. In traditional delayed coking processes, these heavyaromatics are either recycled to the heater inlet with fresh feed orretained in the heavy coker gas oil via a deeper cut point. If left inthe coker gas oils, these compounds typically end up as (1)coke-on-catalyst in the downstream processing units (FCCU,hydrotreating, etc.), (2) by-products of downstream process(es) that arerecycled as feed to the coker (e.g. FCCU slurry oil), and/or (3) crackedfeed in high severity processing (e.g. hydrocracking). When cracked, theundesirable sulfur and metals in these compounds typically end up in thecracked finished products. Thus, these compounds are undesirable indownstream processing and are often overvalued by refinery LinearProgram (LP) Computer Models (used to maximize refinery profitabilityvia optimizing process operating conditions).

[0449] In contrast, these heavy, aromatic compounds can help increasethe coker's propensity for high porosity, sponge coke and increase cokeVCM content. Furthermore, these aromatic compounds typically containlower concentrations of sulfur, nitrogen, and metals .(e.g. vanadium &nickel) than the other coke components (asphaltenes and resins). Thus,the concentration of these undesirable elements is also incrementallyreduced in the petroleum coke. In addition, these same heavy, aromaticcompounds typically contain significantly higher concentrations ofsulfur, nitrogen, and metals than other coker gas oils components. Thus,leaving these heavy aromatics in the pet coke (vs. in the coker gasoils) can incrementally reduce the concentration of these undesirablecompounds in the coker gas oils. Since the gas oils are furtherprocessed (hydrocracking, FCCU, etc.) to produce transportation fuels,this may also provide an effective means to further reduce thesecontaminants (e.g. sulfur) in transportation fuels (e.g. diesel),regardless of the improvements in the pet coke qualities and value.

[0450] In the vapor phase, excessive cracking reactions can producesuboptimal product yields and cause limits in coker throughput capacity.In traditional coking processes, cracking reactions continue to occur inthe high temperature vapors coming off the coke mass, until quenched bysteam in the coke drum vapor line and/or the cold feed in the bottom ofthe fractionation tower. This continual cracking of the hydrocarbonvapors can detrimentally impact coker product yields. That is, thisexcessive cracking of hydrocarbon vapors (i.e. “vapor overcracking”)converts high-value, cracked liquids (with 3 or more carbon atoms) tosmaller molecules (primarily methane, ethane, & hydrogen) that can onlypractically be used as refinery fuel gas. This refinery fuel gas oftenhas significantly lower value than the cracked liquid products. In fact,methane, ethane, and hydrogen typically account for over 75% of thedried coker gas (Lb-Moles/Hour) from the fractionation column. Inaddition, vapor overcracking increases the vapor loading of thefractionation system. That is, the cracking of hydrocarbon vapors tosmaller compounds creates more molecules of various hydrocarbon vapors(including cracked liquids) and other gaseous components. This causeshigher vapor flow rates (i.e. lb.-moles per hour) and pressure drops.Thus, vapor overcracking is normally undesirable due to (1) lowerproduct yields of valuable hydrocarbons and (2) the excessive vaporloading of the coker fractionation system, which can bottleneck or limitthe coker throughput capacity. Alternative coker process modificationshave been developed to reduce undesirable vapor overcracking and furtheroptimize coking processes.

[0451] (1) Clarification of Patent Objectives:

[0452] In view of this enhanced theory of operation, furtherclarification of the patent objectives is provided. As noted above, someof the patent objectives include (1) modification of the petroleum cokecrystalline structure and (2) increasing the content of volatilecombustion materials (VCMs) in the petroleum coke. Other patentobjectives were also discussed, but clarification of these patentobjectives is helpful in the following discussion regarding the newdiscovery.

[0453] Coker Operational Changes: Relative to Current Operation

[0454] Current Operation Assumptions: VCM: 10-12wt. %; Shot or PoorSponge Coke

[0455] Examples: Light, Sour Crude; Heavy, Sour Crude

[0456] Modification of the Petroleum Coke Crystalline Structure: Furtherdefinitions

[0457] Sponge Coke: Porous Sponge, Preferable; Dense Sponge, MorePreferable; & Honeycomb, Most Preferable (Technically, But May Not BeEconomically)

[0458] Non-Graphitizable Sponge preferable to Graphitizable Sponge Coke:Lower C/H Ratio, Increased Reactivity, & Improved Carbon AdsorptionCharacter

[0459] Thermal vs. Asphaltic Coke: Further Definition of Heavy AromaticCompounds

[0460] Increasing Coke VCM Content:

[0461] Types of VCMs: Integration in coke; condensed liquid vs.adsorption vs. cross-link, vs. condensation bonding (but not fullyintegrated; bond broken <1700° F.)

[0462] VCM Added via Coke Quench: Adsorbed in Coke; Higher Quality VCM

[0463] Thermal Coke Role in VCM content: Non-graphitizable coke; VCM<1700° F.

[0464] (2) Alternative Perspective of the Exemplary Embodiment:

[0465] Various process options have been discussed that modify cokeroperating conditions and/or procedures to achieve the desiredmodification of coke crystalline structure and higher coke VCM levels.However, decreasing the heater outlet temperature was described as theexemplary coker process modification in many applications. The lowercoking temperature reduces both coking and cracking reactions, primarilyin the liquid phase.

[0466] The types of chemical components in the coker feedstocks play amajor role in determining which cracking and coking reactions decreasemore significantly with the lower coker operating temperatures. Ingeneral, the hierarchy of cracking reactions usually occurs in thefollowing order (most reactive to least reactive): paraffins >linearolefins >naphthenes >cyclic olefins >aromatics. The crackability alsotends to increase with molecular weight (or boiling range). Afterremoval of side chains, cracking of the very stable aromatic compoundsapparently requires the highest heat of activation. In fact, basicaromatic ring structures (e.g. benzene) normally require temperatureshigher than normal coker temperatures (or catalysts) to thermally crackthe strong chemical bonds of these compounds. Thus, the lower molecularweight aromatics will often pass through the coker without furthercracking. Usually, these lighter aromatics are either (1) cracked indownstream catalytic cracking processes or (2) become part of thefinished product blendstocks without further cracking. Consequently,cracking of the heavier, polycyclic aromatics is normally thepredominant type of cracking reaction affected by lower coker operatingtemperatures (i.e. lower heat available). As such, the very heavyaromatics will be the primary feed components that are less likely tocrack at lower coker temperatures. Thus, these feed components tend toremain in the coke mass due to lower heater outlet temperatures.

[0467] In contrast, the endothermic coking reactions (i.e. condensation& polymerization) for these heavier aromatics generally require loweractivation energies than their competing cracking reactions. Otherwise,the cracking of these heavy aromatics would preferentially occur atlower operating temperatures, instead of the predominant coking of thesearomatics. Thus, the coking reactions of heavy aromatics are lessaffected by the lower heater outlet temperatures (vs. crackingreactions). In this manner, these heavy aromatics will preferentiallycoke at lower coker temperatures, as long as the temperature drops arenot excessive. Thus, heavy aromatics (e.g. PAHS) that are not cracked,but coked via endothermic reactions (e.g. condensation andpolymerization) and thermal coking. As such, the coking of these heavyaromatics (i.e. thermal coke) apparently decreases the ratio (R) ofasphaltic to thermal coking sufficiently to form a porous, sponge coke.Also, heavy aromatics that are not cracked nor coked can providelow-quality VCMs in the pet coke. In this manner, some or all of thebenefits of the present invention can be achieved by changing oneindependent operating variable: decreasing the coker heater outlettemperature by 5 to 50° F, preferably 5 to 25° F. (most preferably 5-15°F.) with a corresponding drop in coke drum outlet temperature of 5 to80° F; preferably 5 to 40° F. That is, the heater outlet temperature isreduced by 5 to 50° F. from the traditional coker operation thatproduces 8-12 wt. % VCM (Volatile Combustible Materials) for a specificcoker feedstock and design, with other operating control variables heldconstant. Again, the reduction in coke drum vapor line temperature isnot necessarily equal to the reduction in heater outlet temperature dueto the changes in the types of endothermic reactions taking place in thecoke drum. The relationship of reduction in heater outlet temperature,increase in coke VCM, change in coke crystalline structure, and cokedrum vapor line temperature can vary substantially in significantlydifferent coker feedstocks. Though this theory of operability can behelpful in understanding the proper operational changes, the currentinvention should not be bound by it.

[0468] Other benefits of decreasing the heater outlet temperature makeit the predominant process modification of the exemplary embodiment.These potential benefits include, but are not limited to (1) improvingproperties of various fuels, (2) reducing fuel usage/costs, (3) reducingmaintenance of heater section, (4) debottlenecking the coker heatersection, and/or (5) improving overall coker product yields. First, U.S.EPA regulations are placing further limitations on the sulfur, metals,olefins, and aromatics contained in the finished fuel products. Thelower coker temperature inhibits formation of olefins and aromatics indownstream products, while retaining more sulfur and metals of the heavyaromatics within the coke. This requires less severe hydrotreating orhydrocracking of coker intermediate product streams. Secondly, thereduction in heater outlet temperature not only reduces fuel usage andcosts per barrel of unit feed, but can also reduce the overall fuelusage/costs. Thirdly, one of the primary sources of coker heater sectionmaintenance is the coking of the heater tubes & associated tubefailures. Lowering the heater outlet temperature can significantlyreduce heater tube coking and the need for steam injection and periodicdecoking (& associated down time). Fourthly, the reduction in cokerheater outlet temperature and associated reductions in feed recyclenormally reduces limits (debottlenecks) in the heater section andprovides greater operational flexibility and higher heater capacity.Finally, the overall effect on coker product yields can provide morefavorable coker profitability, in many cases.

[0469] The overall change in coker product yields can vary significantlyamong refineries due to (1) design & operation of various process units,(2) differences in integration of process units, (3) refinery crudeslate, and (4) coker feedstocks. As the coker feedstocks increase inasphaltene and resin content, greater quantities of aromatics willgenerally be required to achieve the proper asphaltic coking to thermalcoking ratio (R) for the desired porous, sponge coke. With some cokerfeedstocks, the minor reduction in heater outlet temperature does notsignificantly impact the coker product yields. In these cases, theincreased value of the petroleum coke can more than offset anyreductions in other coker products. For other feedstocks, the requiredreduction in heater outlet temperature (e.g. >15° F.) can detrimentallyimpact the coker operation and/or product yields (e.g. substantial lossof other compounds from the heavy coker gas oil). These coker feedstockstypically have low °API gravity (e.g. <10) and high Conradson Carbonresidue (e.g. >16%). In many (but not all) cases, this situation mayrequire other coker process modifications to achieve some or all of theadvantages of the present invention and/or offset detrimental productyields for economic reasons. The °API gravity is common density propertyin the oil industry as determined by the following formula:°API=(141.5/specific gravity)−131.5. Conradson Carbon is an indicationof the coke residue potential for crude oils or petroleum derivatives,and is determined experimentally via ASTM D189-52. Both °API andConradson Carbon are common oil industry terminology.

[0470] (3) Additional Embodiments to Achieve Patent Objectives:

[0471] Various coker operational changes have been described thatachieve (1) modified crystalline structure, (2) higher pet coke VCMs,and/or (3) other advantages of the current invention. These operationalchanges were discussed, recognizing that various combinations of otheroperational changes were possible. That is, the present invention is notlimited to changes in heater outlet temperature, but includes otheroptions. The following provides further detail about potential operatingchanges with respect to the heavy aromatics theory of operation. Thisalternative perspective also provides clarification of the exemplarymethods.

[0472] The present invention contemplates any coker equipment and/orprocess modifications (or any combination thereof) that selectivelyencourages the retention of certain heavy hydrocarbons (primarilypolycyclic aromatic hydrocarbons) in the coke mass to achieve some orall of the objectives such as: (1) modified coke crystalline structure(porous, sponge coke, preferably with greater carbon adsorptioncharacter) and (2) increased coke VCM content. The amount of heavyaromatics or other hydrocarbons that remain in the coke mass areprimarily dependent on the local operating conditions; the coke drum, inparticular. The primary local operating conditions that selectivelyretain the heavier aromatic hydrocarbons include: lower coke drumtemperature, higher coke drum pressure, reduced cycle times, coker feedmodifications, change in coker recycle rate, and potential catalystadditives. The selectivity of any process modifications can vary fromrefinery to refinery due to variability in coker design, operation, andfeedstocks. The degree of selectivity for each coker equipment and/orprocess modifications can also vary and does not require highselectivity (e.g. >80%) to be sufficiently effective.

[0473] Various operational controls can be modified to achieve thedesired retention of coker feed components in the coke mass and theother advantages of the present invention. The four primary independentcontrol variables for the traditional delayed coker operation are (1)heater outlet temperature, (2) fractionator pressure, (3) fractionatorhat temperature, and (4) residual carbon in the coker feedstocks. Otheroperational variables are directly or indirectly affected by (ordependent upon) changes in these control variables. For example, theamount of heavy aromatics or other hydrocarbons that remain in the cokemass are dependent on the local coke drum temperatures. As noted above,the heater outlet temperature indirectly affects the coke drumtemperature, depending on the remaining degree of endothermic crackingand coking reactions. Increasing fractionator pressure is an alternativecontrol that can increase coke drum pressure to achieve some or all ofthe advantages of the present invention. For given coker feedstocks, thefractionator hat temperature has a limited impact on the amount of heavyhydrocarbons left in the coke mass. That is, heavy aromatics leaving thecoke drum go to either heavy gas oil or recycle, depending onfractionator hat temperature. Finally, as noted above, altering thecoker feedstocks can also be used to achieve some or all of theadvantages of the present invention.

[0474] a. Coke Drum Temperature:

[0475] In the prior art, coke drum temperature (measured unquenched inoverhead vapor line) is typically maintained at temperatures of >820° F.(preferably 830-870° F.) to achieve coke VCM content <12 wt. %. Thecurrent trend is to maximize coke drum temperature to heater and/or cokehardness limits. In contrast, the coke drum temperature can be reducedfrom current operation by 5-80° F. (preferably 5-40° F. ) to achievesome or all of the advantages of the present invention by (1) reducingundesirable cracking and/or coking reactions and/or (2) condensingheavier hydrocarbons to remain in the coke drum until cracked or coked.That is, drum outlet temperatures of the current invention can rangefrom 750 to 865° F. (preferably 770 to 825° F.). More importantly,however, for a particular coker and coker feed blend, the coke drumtemperature is reduced by 5-80° F. (preferably 5-40° F.) from coke drumtemperatures that achieve coke VCM content <12 wt. %. Reducing theheater outlet temperature can do either or both. Alternatively,chemically quenching the endothermic cracking and/or coking reactionscan achieve the former. On the other hand, a thermal quench within thecoke drum can have a net effect of doing either or both, as well.Finally, other methods that effect coke drum temperature (e.g. reducedinsulation) can also produce some desired effects.

[0476] a1. Heater Outlet Temperature:

[0477] As discussed previously, the reduction of the heater outlettemperature may be the desired operational change to achieve some or allof the advantages of the present invention. In many coker operations, amodest reduction in heater outlet temperature of 5-50° F. (preferably5-25° F.) can be sufficient to achieve the desired coke drumtemperature, its associated increase in VCM and the additional thermalcoking required to produce a highly porous, sponge coke. However, inother coker applications, the reduction in heater outlet temperaturerequired to achieve these benefits can be excessive. That is, technicaland economic limitations in certain applications can be prohibitive inthe sole use of reduced heater outlet temperature to achieve theadvantages of the present invention. These limitations can include, butare not limited to, (1) excessive drop in cracking (e.g. napthene ringsare difficult to crack at temperatures <900° F.), (2) insufficient heatavailable for coking reactions (e.g. significant pitch-like material vs.coke), and/or (3) significant detrimental impacts on yields of crackedliquids and associated profitability losses. In these situations, othercoker process changes of this invention can be used in lieu of or incombination with a less severe reduction of heater outlet temperature.

[0478] a2. Coke Drum Chemical Quench:

[0479] The benefits of injecting certain carbonaceous materials into thecoker feedstock were briefly described earlier. When cracked, thesecarbonaceous materials generate low molecular weight compounds (e.g.carbon monoxide) that can alter the cracking and coking reactions in amanner that inhibits shot coke formation (i.e. encourages sponge coke).For example, certain plastics can produce free radical hydrogen that canpotentially terminate cracking mechanisms downstream of the primaryreaction zone and inhibit vapor overcracking. These free radicals canalso assist in thermal coking mechanisms. Apparently, this chemicalquench of the cracking reactions and the increased thermal cokingreactivity can improve coke crystalline structure and potentiallyincrease coke VCM. This type of chemical quench can be effectively addedto the coker feed at rates of (0.1 to 20 wt. % of feed; preferably 0.1to 8.0 wt. % of feed). In a similar manner, hydrogen can be injecteddownstream of the primary reaction zone with similar results. This otherembodiment is discussed in more detail in the section on vaporovercracking.

[0480] a3. Coke Drum Thermal Quench:

[0481] A thermal quench of 5-80° F. (preferably 5-40° F.) near the vaporexit of the coke drum (vs. vapor line quench) can be a desired method insome cases to achieve some or all of the benefits of the presentinvention. The primary intent of this thermal quench within the cokedrum is an effective condensing of the heaviest vapors back into thecoke drum. These heaviest vapors are typically heavy aromatics (e.g.PAHs) that undergo further coking or cracking with additional residencetime in the coke drum, particularly at the end of the coking cycle. Theselective condensation of the heaviest vapors (vs. lighter recyclevapors or heaviest heavy coker gas oil—HCGO components) can selectivelypromote some or all of the benefits of the present invention with thevapors of lowest value. Various quench media can be used, but cooledheavy coker gas oil (e.g. product or fractionator pump-around refluxsystem) may be suggested to mitigate vapor loading problems in thefractionator section. In this manner, a thermal quench can also be usedto achieve some or all of the advantages of the present invention.Reduction of vapor overcracking may be an added benefit or additionalintent for this thermal quench of vapors.

[0482] The quench media can be introduced into the coke drum via variousmechanical devices. In some cases, the existing anti-foam injectionsystem(s) can be modified to serve both purposes: antifoam and coke drumthermal quench. Existing anti-foam injection systems typically use agas-oil carrier to convey a silicone antifoam, but are often positionedas far from the exit vapor line as possible to avoid silicone carryover.The existing anti-foam system could be modified to increase the gas oilflow rate and/or add other quench media to achieve the desired coke drumtemperature. Other quench media can include, but may be limited to,coker gas oils, various fuel oils, and other chemical compounds thathave desirable characteristics, but limited impacts on the coker drumand fractionator systems. Alternatively, additional or separateinjection lances (1 to 8; preferably 1 to 4) can be mounted near thecoke drum vapor exit(s). Examples of injection lances through boltedflanges are shown in FIGS. 6A-6D. The quench media injection lances 610a, 610 c penetrate the coke drum 620 a, 620 c via reinforced flanges 630a, 630 c. The reinforced flanges can be welded to the top of the cokedrum, following proper ASME procedures to maintain pressure integrity.Likewise, the lances may be properly welded in the flange cover plates.The materials of construction for both injection lances and mountingflanges are sufficient to perform their functions in the coke drumoperating environment. The angle of the flange mountings, the lancemountings, and lance spray nozzles may be designed to sufficiently coverthe vapor disengagement zone of outage areas in each coke drum. That is,the quench media spray(s) of the lances preferably cover the entirevapor flow before exiting the coke drum via coke drum vapor line(s) 640a, 640 c. Furthermore, the injection lances may not extend into the cokedrum more than a predetermined distance, e.g., about 10-15 feet in atypical embodiment, to mitigate potential pluggage with coke. Also, thedesign preferably allows replacement with spare lance(s) during thedecoking cycle should loss of flow occur. Other potential embodiments ofthe coking vapor quench are shown in FIGS. 6E to 6H. In theseembodiments, the vapor quench occurs external to the coke drum 620 e,620 g in the overhead vapor line 640 e, 640 g via injection lances 610e, 610 g. These embodiments can use the force of gravity to convey tothe condensed, heavy hydrocarbons back into the coke drum. However,these quench systems may not be preferred in many cases, due to theirpotential build-up in the vapor line, causing flow restrictions and/orundesirable pressure drops. Ones skilled in the art can develop othermechanical devices that would achieve effective thermal quench of vaporsprior to exiting the coke drum and accomplish some or all of the processadvantages of the present invention. The required flow rates of thechosen quench media can be readily determined by one skilled in the artvia standard engineering procedures and heat balance calculationmethods.

[0483] a4. Reduced Coke Drum Insulation:

[0484] Reducing the degree of coke drum insulation can be used, to acertain degree, to reduce coke drum temperature. In particular, lessinsulation in the upper portion of the coke drums can contribute to thereduction in coke drum outlet temperature (i.e. unquenched vapor linetemperature) without thermally quenching primary cracking and cokingreactions in the lower drum. This option can contribute to thecondensation of the heaviest vapor components (e.g. heavy aromatics)leaving the drum and help reduce vapor overcracking. However, thisoption can also cause localized phenomena with a more pronouncedtemperature gradient near the coke drum shell. This can causeundesirable variability (e.g. less control) in the cracking reactionsand coke crystalline structure.

[0485] b. Coke Drum Pressure:

[0486] In the prior art, the coke drum pressure is typically maintainedbetween 15-30 psig. The current trend is to minimize coke drum pressureto reduce coke yield within the operational limits. In contrast,increasing the coke drum pressure by 3-30 psig (preferably 3-10 psig) isan effective method to condense the heaviest components (e.g. PAHs ) ofthe vapors leaving the coke drum. That is, coke drum pressures of thecurrent invention can range from 15-40 psig (preferably 20 to 30 psig).More importantly, however, for a particular coker and coker feed blend,the coke drum pressure is increased by 3-30 psig (preferably 3-10 psig)from coke drum pressures that achieve coke VCM content <12 wt. %. Thesimplest and most common method for increasing coke drum pressure is toincrease the fractionator pressure by increasing backpressure at the wetgas compressor. However, capacity and other limitations can make othercreative approaches to increase coke drum pressure more desirable,including various mechanisms to control and balance system pressures.

[0487] b1. Fractionator Pressure:

[0488] Increasing the coker fractionator pressure usually increases thecoke drum pressure. The higher drum pressure suppresses the vaporizationof heavier components remaining after cracking and coking of coker feedor recycle. As such, less quantity of the high-boiling hydrocarbons,including heavy aromatics (e.g. PAHs), are transferred from the cokedrum to the coke drum vapors and the coker fractionation column. In thismanner, increasing the fractionator pressure generally leaves more ofthe heavier aromatics in the coke mass within the coke drum. Thus,increasing the coke drum pressure (via controlling the fractionatorpressure) is an acceptable process modification to achieve the benefitsof (1) modified coke crystalline structure and (2) increased coke VCMs.In some cases, this process modification may be preferred due to itssimplicity. However, this alternative can cause compressor overloading,associated capacity limits, and/or some detriment to product yields. Insome cases, other means could be logically employed to increase drumpressure with limited impact on the existing compressor system.

[0489] b2. Alternative Mechanisms to Increase Coke Drum Pressure:

[0490] As noted above, creative alternative approaches can be used toincrease control and/or balance system pressures to increase coke drumpressure. For example, the pressure drop between the coke drum andfractionator could be mechanically increased and controlled. Byincreasing heater outlet pressure (e.g. heater inlet pump(s) and/orinjection steam pressure), coke drum pressure can be increased, to acertain extent, with less impact on the pressures of the fractionatorand downstream equipment. A variety of mechanisms could be used forincreasing and controlling pressure drop between the coke drum andfractionator. The partial coking of vapor lines already increases thepressure drop between coke drum and fractionator by as much as 8-10psig. In a similar manner, a smooth transition orifice spool could bedesigned for insertion in the vapor line downstream of the quench zone.This static pressure drop control would change with vapor flow (i.e.velocity). Alternatively, a variable throat venturi, similar to thoseused in wet scrubber applications, could be developed to achieve betterpressure drop control. However, potential pluggage or other problems aremore likely with this type of device. One skilled in the art can developa suitable solution that addresses the particular needs (risks vs.benefits) of the specific coker application.

[0491] c. Reduction in Cycle Time:

[0492] In the prior art, coking cycle times typically range from 16-24hours. The current trend is to minimize cycle times within equipment,operational, and coke quality (e.g. <12 wt. % VCM) constraints. Incontrast, reducing coking cycle time by 2-12 hours (preferably 4-8hours) can be effective in increasing coke VCM and potentially producedesirable modifications in coke crystalline structure. That is, cokingcycle times of the current invention can range from 12 to 24 hours(preferably 12 to 16 hours). More importantly, however, for a particularcoker and coker feed blend, the coker cycle time is reduced by 2 to 12hours (preferably 4-8 hours) from coking cycle times that achieve cokeVCM content <12 wt. %. Lower cycle times reduce the residence time ofthe cracking and coking reactions. As a result, the VCM content of thecoke increases by approximately 1 wt. % for each 4-6 hours reduction incycle time. Furthermore, an increase in thermal coke production canoccur in coker operations, where the reduction in cycle time has morepronounced effect on cracking versus coking reactions. That is, thecoking of heavy aromatics (e.g. PAHS) is more favorable than theirrespective cracking reactions. In this manner, a reduction in cokingcycle time can be effective in achieving some or all of the benefits ofthe present invention such as: increased coke VCM and modifiedcrystalline structure (porous sponge coke).

[0493] d. Feed Modifications: In the prior art, the coker feeds havegotten progressively worse. Heavier crudes have typically pushed delayedcokers to coking limits (e.g. coker & refinery bottlenecks).Consequently, the current trend is to minimize coker feeds of higherquality (e.g. reducing virgin gas oil content or increasing end pointson virgin & heavy coker gas oils), increasing Conradson carbon of cokerfeeds >22. In contrast, various modifications to the coker feed(Conradson carbon <26; preferably <20) can be used as additional methodsfor achieving some or all of the advantages of the present invention.These modifications can take the form of modified crudes slates, cokerfeed blends, and/or coker feed additives. Modifications of the cokerfeed can integrate more aromatics (Aromatics with propensity to coke >40wt. % of coke; preferably >60 wt. % of coke) in the coke mass. That is,the addition of coker feedstocks with higher aromatic contents willgenerally increase thermal coking and decrease the asphaltic coking tothermal coking ratio (R) in the coke drum. This increased thermal coking(endothermic) can also have a significant impact on the coke drumtemperature. In this manner, coker feed modifications can produce thedesired crystalline structure and potentially increase coke VCM contentvia heavy hydrocarbons not fully integrated in the coke. Coking limitscan be mitigated by operational benefits of the current invention (e.g.decreased cycle times). The degree of feeds blend modification canreadily be determined by one skilled in the art for a specificrefinery/coker application, based on coker design (and coking limits),available coker feeds, relative impact on Conradson Carbon, and overallimpact on coke quality.

[0494] d1. Modified Coker Feed Blends and Crude Slates:

[0495] The current coker feed blend can be composed of differentproportions of the same feedstocks to produce a blend with higherconcentration of heavy aromatics. Alternatively, the current coker feedblend could be blended with other coker feedstocks (e.g. 1-50 wt. % ofthe total blend; preferably 3-10 wt. %) to produce a desired coke feedblend. These coker feedstocks would include, but should not be limitedto, aromatic crude oils, thermal tars, coal tars, pyrolysis tars, coaltar pitch, heavy virgin gas oil (HVGO), furfural extracts, phenolextracts, and slurry oils (e.g. decanted oil from the FCCU). Otherintermediate product, byproduct, or waste streams that contain asignificant portion of aromatic compounds (e.g. >30 wt. %;preferably >50 wt. %) could also be used as coker feed blendstocks. Inthis manner, modification to the coker feedstocks can be an effectivemeans to partially or fully achieve the benefits of the presentinvention. The same objective could also be achieved by increasinghigher quality crudes in the crude blend: lighter, paraffinic, and/oraromatic. In addition, the heavy virgin gas oil (HVGO) can be addeddirectly to the coker feed. However, lowering the cut point in thevacuum tower and leaving only the heaviest HVGO in the vacuum resid(i.e. coker feed) would be preferable. This vacuum distillation changehas the added benefit of incrementally improving FCCU feed quality ofthe HVGO.

[0496] d2. Coker Feed Additives:

[0497] As noted previously, certain carbonaceous compounds can be addedto the coker feed to enhance the ability to achieve some or all of theadvantages of the present invention. The breakdown of these carbonaceousmaterials apparently produces intermediate compounds that inhibit shotcoke formation and favor thermal coking. These carbonaceous additivesinclude, but should not be limited to, coal wastes, wood wastes,cardboard, paper, plastics, and rubber. These solid carbonaceousmaterials may be finely pulverized (>80 wt. % <100 mesh) and may, forexample, be added to the coker heater feed via methods described inexpired U.S. Patent 4,096,097. Additional details, particularly forplastics and rubber, are provided later. (See Plastic/Rubber Addition tothe Delayed Coker: Exemplary Embodiment).

[0498] e. Coker Recycle Rate:

[0499] In prior art, coker recycle rates are typically maintained at10-35 wt. %. The current trend is to minimize coker recycle withinoperational constraints (e.g. coke drum heat balance) to minimize cokeyield. In contrast, modifying coker recycle rates can be effective inpromoting thermal coke reactions and potentially increasing coke VCM. Inthe prior art, decreasing the coker recycle rate has been used todecrease coke yield by increasing the heavy components of the coke drumvapors drawn into the heavy coker gas oil. Conversely, increasing therecycle rate leaves these heavier components of the HCGO (e.g. heavyaromatics) in the recycle stream and increases yields of thermal coke.Alternatively, other operational methods of the current invention canpreferably leave these heavier vapor components in the coke drum andreduce coker recycle rate. The resulting lower recycle rates can oftenprovide sufficient heater and coke drum capacity to add coker feeds withsignificant aromatic content, which tend to increase thermal coke.Consequently, these three methods of modifying coker recycle rates maybe used to achieve some or all of the benefits of the present invention.

[0500] e1. Feed Alternatives with Reduced Coker Recycle Rate:

[0501] In the prior art, the coker recycle rate has often been reducedto decrease coke yield for a given feed. by increasing the fractionatorhat temperature. The fractionator hat temperature is the temperature ofthe vapors rising to the gas oil drawoff tray in the fractionator.Increasing the hat temperature increases the gas oil end point, theupper end of its boiling range. This increases amounts of higher boilingcomponents (e.g. 900° F. to 925° F.) in the heavy coker gas oil. Theincorporation of these higher boiling point components into the heavycoker gas oil (HCGO) lowers the coker recycle rate. This reduction ofcoker recycle rate is limited by (1) acceptability of heavier HCGOcomponents in downstream processing and (2) heat requirements of thecoke drum to complete desirable cracking and coking reactions. In thelatter, the additional heat carried by the heated recycle stream intothe coke drum is often critical to provide sufficient heat for crackingand coking reactions. A heat balance around the coke drum reveals:

Q _(in)=(FF+R)×avg. Cp×T _(in) =Q _(out) +Q _(cracking) +Q _(coking) +Q_(walls) +Q _(quench)

[0502] Where Q=associated heat values; FF=fresh feed; R=coker recyclerate; avg. Cp=average combined feed (i.e. FF+R) heat capacity at Tin;and Tin=coke drum inlet temperature. This simplified formula shows thatsignificant reductions in coker recycle rates can have substantialeffects on the heat available for cracking and coking reactions, if theheater outlet temperature remains constant. Thus, increases in heateroutlet temperature are often implemented to offset any reductions cokerrecycle rate. Consequently, heater limitations and the feed's propensityto coke typically limit reductions in coker recycle rate in the priorart. However, reductions in coker recycle rate generally makes moreheater feed capacity available. This feed capacity can be used forincreased feed rate, if available. Alternatively, various coker feedalternatives (advocated earlier) can be added to the current feed topotentially increase thermal coke and coke VCM. Either or both of thesealternatives can significantly increase the heat available in the cokedrum and offset the loss of recycle rate. That is, even with lower heatcapacities than the traditional recycle materials, these coker feedalternatives (e.g. plastics, rubber, etc.) can provide sufficient heatin many cases. Also, these coker feed alternatives often have lesscoking propensity and require less heat to be cracked to valuablecracked liquid products.

[0503] e2. Increased Coker Recycle Rate:

[0504] Conversely, increasing the coker recycle rate by 3-30 wt. %(preferably 3-15 wt. %) can achieve some or all of the advantages of thepresent invention by increasing heavy aromatics and thermal coking inthe coke mass. That is, coking recycle rates of the current inventioncan range from 5 to 50 wt. % (preferably 15 to 35 wt. %). Moreimportantly, however, for a particular coker and coker feed blend, thecoker recycle rate is increased by 3-30 wt. % (preferably 3-15 wt. %)from coker recycle rates that achieve coke VCM content <12 wt. %.Decreasing the fractionator hat temperature leaves the heaviercomponents of the HCGO (e.g. PAHs) in the fractionator bottoms that arerecycled with fresh feed to the coker heater. As such, decreasing thehat temperature increases the coker recycle rate. In this manner, thecoker recycle goes through the heater and coke drums until it is either(1) converted to lower boiling range components that leave with theheavy coker gas oil (or other cracked products) or (2) integrated intothe coke mass. Since this additional recycle tends to be primarily heavyaromatics, the increased coker recycle rate tends to increase thermalcoking and potentially increase coke VCM, depending on the level of cokecarbonization. In addition, the reductions of these heavier componentsin the HCGO make it a higher quality feed for downstream processing(e.g. FCCU). Increases in coker recycle rates of this manner are limitedby heater capacity, coke drum capacity, and/or recycle stream'spropensity to coke.

[0505] e3. Optimal Recycle Rate and HCGO Quality:

[0506] Another process option may achieve some or all of the benefits ofthe present invention while decreasing coker recycle rate and improvingHCGO quality. Other operational methods, previously advocated in thecurrent invention via (e.g. lower drum temperature or higher coke drumpressure), can condense the heaviest components in the coke drum priorto reaching the fractionator. Thus, these heaviest components do not endup in either of the HCGO (higher quality) or the recycle stream (lowerrecycle rate). Again, it should be noted that these heaviest componentsof the coke drum vapors are significantly heavier than the heaviestcomponents of the HCGO, as determined by the fractionator hattemperature. Thus, the limits of decreasing coker recycle rate aresimilar to decreasing coker recycle in the prior art: heat balancelimitations. However, in this method of the current invention, there isgreater operational flexibility: (1) lower recycle rates without lowerHCGO quality (i.e. due to higher hat temperature), (2) higher HCGOquality (i.e. due to lower hat temperature) with constant recycle rates,or (3) other combinations of HCGO quality and recycle rates. Preferably,the condensation of the heaviest recycle components (e.g. PAHs) in thecoke drum allows a decrease in hat temperature (3-40° F.; preferably 5to 20° F.) to increase HCGO quality, while still reducing the recyclequantity with improved quality (e.g. less heater coking propensity).This reduced recycle rate provides (1) reduced heater severity (e.g.less fuel & less heater tube coking), (2) availability of more heaterfeed capacity and/or (3) various coker feed alternatives (advocatedearlier) can be added without exceeding heater limits. In this manner,some or all of the benefits of the present invention can be achieved viaa modest reduction in the heaviest components of the heavy coker gasoil. In addition, the coker recycle rate can be reduced whilemaintaining proper coke drum heat balance and improving HCGO quality.One skilled in the art can achieve optimal (1) condensation of heaviestrecycle components, (2) HCGO quality, (3) recycle rate, and/or (4) feedadditives via empirical studies (e.g. pilot plant) for specific cokerdesign, feed blends, and operating objectives (e.g. LP Model). Theprimary operating variables would include (1) quenched coke drumtemperature, (2) coke drum pressure, and (3) hat temperature.

[0507] f Catalytic Additives:

[0508] Finally, catalytic compounds can be added to the coker feedand/or the coke drum downstream of the primary reaction zone to enhancethermal coking reactions. These catalysts will allow the endothermicthermal coking reactions to take place with lower heat of activation andoften at lower temperatures. Consequently, these thermal coking(condensation and polymerization) reactions can preferentially proceedversus endothermic cracking reactions that compete for available heat ata given drum temperature. For example,

[0509] As noted above, various coker process modifications can beemployed as alternatives to achieve some or all of the advantages of thepresent invention such as: (1) modified coke crystalline structure withgreater carbon adsorption character and (2) increased coke VCM content.That is, lower coke drum temperature (via heater outlet temperature,and/or drum thermal quench), higher coke drum pressure (via fractionatorpressure, feed pressure, controlled pressure drops, and/or othermechanism), coker feed modifications (via crude slate, coker feedstocks,and/or various feed additives), recycle rate (via hat temperature orreductions in heavy aromatic compounds left on coke vs. in recycle),and/or catalyst additives can effect the desired retention of certainhydrocarbons in the pet coke. Though each will work to a limited degree,their effectiveness will vary from refinery to refinery. As a result,any combination of these alternatives can be used to effectively achievesome or all of the advantages of the present invention. However, theireffects may not necessarily be additive. In certain situations, theoptimal value(s) of the operating variables may lie outside the rangesspecified above due to the combined effects or anomalies of an atypicalcoker system. Thus, standard engineering principles and practices ofthose skilled in the art (including pilot plant studies) may benecessary to determine the optimal combination and their application foreach refinery system.

[0510] In each specific coker application, one skilled in the art canachieve some or all of the invention benefits through the use of any oneor combination of the process options described herein. The optimalcombinations and degree of utilization of these process options can bedetermined by applying engineering principles & practices with thisinformation and the proper characteristics of the coker design,operation (including history and objectives), and available coker feeds.Modest testing (e.g. laboratory and/or pilot plant) may be necessary todetermine certain characteristics and operating effects for particularcoker feeds. This is consistent with typical refinery practice forevaluating any significant change for coker operations.

[0511] B. Novel Process Modifications to Reduce Vapor Overcrackinq

[0512] (1) Quench Cracking Reaction in Vapor:

[0513] Various means to quench the cracking reactions of the delayedcoking process were briefly described earlier. One such mechanism wasthe introduction of certain plastics that released hydrogen, whencracked. The purpose of the following section is to describe othermechanisms that accomplish the same objective. The introduction ofchemical agents that release hydrogen or other free-radical species(e.g. low-molecular weight) can terminate cracking reactions bysatisfying the electron structure of intermediate free-radical speciesthat are active in the cracking reaction mechanism due to theirinstability. Hydrogen may be the preferred free-radical because it maybe more likely to terminate the reaction mechanism rather than initiatesome additional cracking. These chemical agents should not be limited toplastics, and include rubber compounds, ammonium compounds, etc. Thesecompounds tend to release hydrogen due to cracking of the chemical agentat the operating conditions of the coking process. The release ofhydrogen in the primary cracking zone can prematurely terminate liquidscracking and be very detrimental to the primary objective of the cokingprocess. Thus, the hydrogen is ideally released downstream of theprimary cracking zone. Consequently, the primary mechanisms, presentedhere, inject chemical agents directly into the vapor phase above thesurface of the semi-solid coke mass. There are various methods tointroduce these chemical agents, but the an exemplary method would use amodified drill stem system. In addition, an exemplary embodiment forthis vapor overcracking quench will be discussed in the followingsections.

[0514] a. Chemical Quench:

[0515] The injection of chemical agents to satisfy the electronstructure of the reactive, intermediate free-radicals (e.g. chainreactions) is an effective way to stop the cracking reactions in thevapor phase. Chemical agents that serve this purpose would includehydrogen, acids, and other chemicals that act as electron donors or canbe easily converted to free-radicals. Similar to plastics (discussedearlier), other chemical agents can be injected with the feed thatrelease hydrogen (thermally or otherwise) downstream of the primarycracking zone. In this manner, the chemical agents indirectly providehydrogen to satisfy the electron structure of the free radical(s). Thatis, these chemical agents effectively react with intermediatefree-radicals and make them substantially less reactive. As a result,the cracking mechanism is terminated or quenched. Likewise, otherchemical agents can release free radicals (other than hydrogen), whichreact with the vapor compounds to terminate or quench vaporovercracking. Similarly, these and other chemical agents can be addeddownstream of the primary cracking zone. These chemical agents eitherreact directly or via an intermediate (e.g. free radical) to quenchfree-radicals and terminate cracking, preferably in the vapor phase.

[0516] b. Thermal Quench:

[0517] The injection of various quench media can also be effective inreducing the vapor temperature and quenching the cracking reactions inthe vapor phase. Quench media can include, but should not be limited to,water, steam, and liquid hydrocarbons (preferably with high boilingrange and high heat of vaporization). The degree of quench mediaaddition is typically determined by the desired cooling of vapors from 5to 80 degrees Fahrenheit, preferably 5 to 40 degrees Fahrenheit. Thislevel of cooling may be sufficient to thermally quench excessive vaporcracking reactions, as well as condense heavy hydrocarbon vapors thatwould otherwise exit the coke drum. Water may be preferred over steam tominimize water required (i.e. water vapor in the exiting process gasstream) via the cooling effect of the heat of vaporization of water.However, at high coke drum temperatures, careful design of the injectionmethod may be required to avoid premature vaporization of the water (orother liquids) and expansion or pressure problems. Alternatively, highmolecular weight, liquid hydrocarbons (e.g. coker gas oils) may be thepreferred cooling medium due to their high heat of vaporization perpound mole and their tendency to remain a liquid at coke drumtemperatures with higher pressures prior to injection into the cokedrums. This temperature quench can have the added benefit of reducingthe heavy hydrocarbon vapors (preferably aromatics) that are preferablykept in the coke mass (discussed previously in section: Coke DrumThermal Quench). That is, these heavy aromatic vapors exiting the cokedrum can be condensed in a manner similar to an increase in drumpressure or the thermal quench systems exemplified by FIGS. 6A-6H.

[0518] c. Injection Method:

[0519] The injection of these chemical agents into the vapor phase ofthe coking cycle (vs. decoking cycle) in the coke drum can beaccomplished by various methods. Ideally, this coke drum quench in thecoking cycle would occur at the interface of the coke-foam and theproduct vapors. From a practical standpoint, the injection of the quenchmay have to occur in various levels of the coke drum with the means toclean the injection ports on a regular basis without coker unitshutdown. As a minimum, quench injection at the top of the coke drum inthe outage area would be needed. This option was discussed in the CokeDrum Thermal Quench section, noted above (e.g. FIGS. 6A-6H).Conceivably, even the injection of quench media with the coker feed atthe base of the coke drum would quench the coker and cracking reactionssimilar to a reduction in feed heater temperature. However, thisinjection method would quench cracking and coking reactions in both theliquid and vapor phases. This would be similar to visbreaking technologyand can substantially change the coker product yield distribution.

[0520] Certain injection methods (e.g. minimum & preferred) can havebeneficial side effects. Injection into the foam layer on top of thecoke mass may also act as anti-foaming agents. That is, the injection ofhigh-pressure hydrogen, gas oils, and/or steam can disperse bubbles viaturbulence breaking liquid surface tension. Conceivably, additionalanti-foaming agents could also be injected with the thermal and/orchemical quench media to achieve even less foam.

[0521] An exemplary method of injection would use a modification of theexisting drill stem, which is currently used for hydraulically cuttingthe coke in the decoking cycle. A totally separate, modified drill stemwould be most preferable. The drill stem design would be modified toallow injection of the chosen quench media (chemical and/or thermal).Depending on the media, drill stem modifications can include, but shouldnot be limited to:

[0522] Design: Size & mechanics determined by media type (e.g. phase)and flow requirements

[0523] Spray Nozzle Design: Size & angle(s) determined by spray patternto cover desired area

[0524] Materials of Construction: Withstand coking cycle operatingconditions;

[0525] temperature, pressure, etc. (e.g. length limited due to torsionalstresses in high operating temperatures)

[0526] Improvements in materials technologies (e.g. composites) canoptimize design

[0527] Drill Stem Cooling System: cooling media passing through drillstem to dissipate excess heat

[0528] For example, steam/N₂ flowing in annulus of concentric-pipe drillstem (e.g. split-ring)

[0529] This modified drill stem design can require advanced drill stemmetallurgy to withstand operating conditions of the coking cycle. Also,the modified drill stem would require a special sealing apparatus toprevent leakage at the interface with the upper drum head at highpressures. Fortunately, the weight of the drill stem will counter theupward force of the pressure in the coke drum, and require lower forcesto maneuver it vertically. Modern sensing technology and/or computersimulations, based on process inputs, can accurately control thedistance between the drill stem and the top of the semi-liquid cokemass. As technology progresses in these areas (e.g. composite materialsscience, sealing, and coke level sensing technologies), the use of amodified drill stem will become increasingly advantageous.

[0530] The modified drill stem is employed by a system that is similarto the current decoking system. First, the modified drill stem would bemaneuvered through its functions using the coke drum derrick. That is,the modified drill stem can be connected, lowered, raised, and rotatedusing similar mechanisms employed by the existing decoking drill stemsystem. Preferably, the modified drill stem does not require rotationalmotion to avoid undesirable, torsional stresses. The major difference,in this regard, will be the addition of the sealing mechanism withbolted flange cover. Secondly, modified drill stem connections to themedia supply system (e.g. pump) would be similar to decoking drill stemconnections to high-pressure water system.

[0531] An example of the modified drill stem system for a coke drum witha side draw vapor line is shown in FIGS. 7A-7B. In this equipmentdiagram, the modified drill stem 710 passes through a sealing apparatus715 mounted on the cover of a reinforced flange 720 in the center of thecoke drum. Normally, this may be the same flange used for the existingdrill stem to drill out the coke in the decoking cycle. At the end ofthe decoking cycle, the existing coke drum derrick 740 is typically usedto position the modified drill stem. Initially, the modified drill stemis normally retracted with sealing apparatus 715 welded to flange platenear the spray nozzle end. After the flange is properly bolted and thedrum is pressure checked, the modified drill stem is lowered into thedrum to its maximum extension. During this descent in the drum, themodified drill stem can be designed to provide additional benefit ofmoderating coke drum warm-up (e.g. steam injection). As the coking cyclebegins, pressurized quench media is injected into the coke drum abovethe coke mass via spray nozzle(s) 750. An automated control system,designed for each specific coker, would be used to assure that themodified drill stem would be moved vertically upward (i.e. retracted) ata rate that maintains at least a minimum distance (e.g., 2-20 feet;preferably 5-10 feet) above the coke mass, as the coke drum fills. Thisminimum distance can depend on the anti-foaming effect of the quenchmedia. As noted previously, certain chemical additives in the quenchmedia can increase the anti-foaming effect. The automated control systemwould preferably have fail-safe design modes and operational proceduresto assure the modified drill stem does not get stuck. The high-pressurenozzles and rotational motion of the modified drill stem (e.g. similarto decoking drill stem) would be designed to optimize spray coverage ofthe cross-sectional area of the coke drum. Full spray coverage of thedrum cross-sectional area is not necessary to achieve desirable results.That is, cooler temperatures near the drum walls and quench mediadiffusional effects will help the quench (chemical and/or thermal) asthe vapors move upward in the coke drum. At the end of the coking cycle,the modified drill stem is fully retracted. After cooling anddepressurizing the coke drum, the flange is unbolted and the existingdrum derrick 740 is used to extract the modified drill stem. Maintenanceof the modified drill stem system can be performed during the decokingcycle. Spare modified drill stem systems are recommended to allowsufficient maintenance time.

[0532] A critical element of this system is the sealing apparatus 715.An example of a potential sealing mechanism is also shown in more detailin FIG. 7B. This diagram shows a double mechanical seal used for sealingrotating shafts in high-pressure systems. Due to the high temperatures(e.g. extracting modified drill stem from hot coke drum), carbon and/orceramic materials may be required for sealing faces. High temperaturealloys may also be required for the metal components. The use of aninert, pressurized liquid or purge gas can be preferable to balance drumvapor pressures within the seal, and mitigate leakage into and/or out ofthe sealing apparatus. In addition, a specially designed cooling systemfor the sealing apparatus may be preferable to dissipate heat fromretracting the modified drill stem from the hot coke drum. To a certainextent, the purge gas/liquid to balance pressure can also be used todissipate heat, as well. One skilled in the art of sealing rotatingshafts can develop a suitable sealing apparatus for each coker system.Improvements in sealing technologies can optimize the design required toachieve desired results.

[0533] In coke drums with center draw vapor lines, the vapor lineconnections would have to be modified to accommodate the modified drillstem during the coking cycle and subsequent exchange during the decokingcycle. One skilled in the art can design the appropriate vapor linemodifications (e.g. special flanged spool) for each specificapplication. Similarly, ones skilled in the art can develop othermechanical devices that could achieve effective quench (chemical and/orthermal) of the vapor cracking reactions and accomplish the processadvantages of the present invention.

[0534] (2) Exemplary Embodiment to Reduce Vapor Overcracking:

[0535] A combination of both chemical quench and thermal quench ispreferable. This combination quench can offer synergistic effects andmaintain t h e desired results with a lower contribution required byeach. In an exemplary embodiment, hydrogen gas and condensed coker gasoil may be injected via an exemplary injection method into the coke drumat the interface of the semi-solid coke mass, or a reasonable distanceabove it (e.g. above coke foam). The quantity of hydrogen addition willvary depending on coker feedstocks, designs, and coker operations, butshould typically be in the range of 0.1 to 10 weight percent of thecoker feed; preferably 0.1 to 1.0 wt. %. The quantity of coker gas oilwill depend on the desired temperature reduction (5-80° F.; preferably5-40° F.) and the coke drum and coker gas oil temperatures. These quenchmedia can be injected in two separate streams. The cooled coker gas oilwould flow through the center of a modified, drill stem withconcentric-pipes. The cooled hydrogen gas would flow in the outerannulus to provide heat dissipation and insulation to prevent excessivevaporization of coker gas oil in the modified drill stem. The heating ofthe hydrogen would also increase the probability of hydrogenfree-radicals, but higher pressures would need to be accommodated in thedesign (e.g. spray nozzle). Preferably, two parallel, flat spraypatterns would emanate from the modified drill stem in all directions(i.e. hydrogen gas on top & coker gas oil liquid on bottom). The mediaflows & pressure and the spray nozzles' number and design will determinethe spray coverage and angles. The spray angle 60 to 135 degrees(preferably 90° to 120°) from the vertical, modified drill stem. A sprayangle slightly downward (from perpendicular to the modified drill stem)is preferable to compensate for upward vapor flow effects as the mediaextends further (radially) from the modified drill stem. One skilled inthe art can make the necessary engineering calculations and designmodifications to address the particular needs of each application of thecurrent invention.

[0536] (3) Other Embodiments:

[0537] The current invention contemplates other embodiments using anexemplary injection method to achieve the goals previously stated. Thishydrogen free-radical quench can be less desirable, in some cases, dueto excessive hydrogen requirements, that overload the fractionatorand/or compressor systems. In some cases, the temperature quench can bethe desired embodiment to achieve both (1) reductions in vaporovercracking and (2) condensation of heavy aromatics that would bepreferably left in the coke, as noted above. These other embodimentsinclude, but should not be limited to:

[0538] 1. Hydrogen gas and liquid coker gas oil in a two-phase injectionsystem (e.g. single-pipe stem)

[0539] 2. Other combinations of thermal quench and chemical quench media(e.g. hydrogen/steam)

[0540] 3. Thermal quench only: Liquid and/or gas quench media (e.g.coker gas oil and/or steam)

[0541] Quantity of temperature quench media (e.g. gas oils, steam,and/or water) depends on the desired temperature drop required to formthe desired porous, sponge coke.

[0542] 4. Chemical quench only: Liquid or gas quench media (e.g.hydrogen and/or ammonia)

[0543] Quantity of chemical quench media: 0.1 to 20 wt. % of coker feed;preferably 0.1 to 2.0%.

[0544] Furthermore, any one or combination of the above can be injectedvia injection methods other than the exemplary injection method.Conceivably, more than one modified drill stem can be active in the samecoke drum and coking cycle. Modified drill stems (e.g. 2 to 8) can beimplemented through a similar number of reinforced flanges in the top ofthe drum to achieve greater spray coverage of the drum's cross sectionalarea. This option may be preferable for some cokers, particularly forcoke drums with an existing center-flange, vapor draw. One skilled inthe art can use standard calculation and design procedures to developthe most practical design for each application of the current invention.The economic incentive for any of these options can be significantlyreduced during periods of high fuel prices, particularly natural gas.

[0545] 4. Further Optimization of Pet Coke's Fuel Properties andCombustion Characteristics

[0546] Various options of the present invention can potentially simplifythe core technology and provide additional process options. An exemplarymechanism of the core technology appears to be based on the followingprocess steps:

[0547] 1. Production of a modified petroleum coke with improved carbonadsorption characteristics

[0548] 2. Use of the petroleum coke's carbon adsorption characteristicsin and/or after the coker process to provide various process optionsthat can optimize its fuel properties and combustion characteristics

[0549] Though this two-step process is believed to describe thetechnical basis for the exemplary core technology, it should berecognized that the current invention is not limited to this. Asdiscussed previously, the core technology may depend significantly oncoker feedstocks and design parameters. As such, the core technology maydeviate from this simplified approach.

[0550] A. Production of Petroleum Coke with Activated CarbonCharacteristics

[0551] As previously discussed, various coker process variables affectpetroleum coke crystalline structure. In addition, various means havebeen described to modify the coker process variables to improve the cokecrystalline structure and increase VCM content. An exemplary embodimentprovides process options to increase the production of sponge coke (vs.shot coke or shot coke/sponge coke mix). The sponge coke of the presentinvention tends to have higher porosity than traditional sponge coke.The higher porosity of the sponge coke crystalline structure of thepresent invention preferably provides one or more of the followingadditional benefits:

[0552] 1. Within limits, greatly improves cutting from drum &pulverization (i.e. HGI >100).

[0553] 2. Enhances adsorption quality of this form of activated carbon(i.e. modified petroleum coke).

[0554] 3. Promotes chemical reactions with petroleum coke due toincreased accessibility via porosity.

[0555] Consequently, the present invention provides additional optionsto produce a very high-porosity sponge coke that offers desirableadsorption characteristics, when properly activated. That is, thefollowing process options can provide a petroleum coke crystallinestructure with carbon adsorption characteristics, including highinternal and external porosities, high surface area, and large porevolume:

[0556] 1. Modify coker process variables to consistently producehigh-porosity, sponge coke; and/or

[0557] 2. Inject certain chemical compounds to increase and/or controlcoke porosity characteristics.

[0558] Depending on the application, a higher degree of petroleum cokeporosity may be the primary goal (versus VCM content). As a result, thesame process variables may be modified to greatly improve or maximizeinternal porosity of the modified sponge coke, within certain technicallimitations. For example, the coke drum temperature is still the primaryprocess variable to affect the desired coke crystalline structure. Ifmaximum internal porosity is desired, an exemplary embodiment mayinclude the lowest drum temperature that consistently produces a solidpetroleum coke with the highest porosity. That is, the drum temperaturewould remain sufficient to prevent unacceptable formation of sticky,pitch-like material and/or excessive VCM content (i.e., not technicallyor economically prohibitive). The addition of aromatic oils (e.g., FCCUslurry oils) may be desirable to further reduce this drum temperatureand increase petroleum coke porosity.

[0559] Other chemical compounds can also be injected to increase and/orcontrol petroleum coke porosity characteristics. Certain chemicalcompounds crack at coking temperatures and provide gaseous componentsthat increase coke internal porosity. The probable mechanism(s) of thisincreased porosity may be (1) passage of gases under pressure risingthrough the solidifying petroleum coke and/or (2) altered coke crystalgrowth. Exemplary gaseous components not only produce increasedporosity, but also allow significant control of pore sizes (i.e.,micropores and mesopores) and volume in the resultant pet coke.Hydrogen, light hydrocarbons (butanes and lighter), and light, inertoxygen derivatives (CO₂l H₂O, etc.) may provide more desirable porositycharacteristics, but other gases can be used, as well. Exemplarychemical compounds for injection include, but are not limited to,recycled plastics, hydrogen, wood wastes, low-rank coals, and steam.Solids may require fine pulverization (e.g. <100 mesh) prior toinjection into the coker. Though several injection points are feasible,an exemplary point of injection is the recycle streams downstream of thefractionator. The quantity of injected compounds can be severely limitedby coker pressure drop, fractionator design, and contaminant limitationsin the traditional coker operation. However, the modified cokeroperation of the current invention typically debottlenecks existingoperations, creating excess coker capacity to be used in this manner.

[0560] An exemplary embodiment for this first process step can includeone or more of the following:

[0561] 1. Minimum coke drum temperature that consistently produces solidpet coke w/o pitch-like material

[0562] 2. Injection of recycled plastics, wood wastes, and/or hydrogenthat optimize porosity characteristics

[0563] As noted previously, desired process conditions may vary with (1)coker feedstocks, (2) coker design and operational constraints, and (3)product constraints. However, this minimum coke drum temperature may belower in most cases, but may still be 750° F. to 850° F. Also, minorequipment modifications (e.g. new coke drum insulation) may be necessaryto assure even temperature distributions across the coke drum. Onesskilled in the art of coking and adsorption media (particularlyactivated carbon) would be capable of determining the optimal design andoperation for particular coker and combustion applications.

[0564] Other embodiments for this first process step include variousother combinations of the coker process variables that (1) achieve thedesired changes in coke crystalline structure and VCM content and (2)provide sufficient adsorption quality in the modified petroleum coke foroptimizing fuel properties and combustion characteristics. Also,selecting and adding certain, low-cost cracking stocks (e.g. variousindustrial by-products and/or non-hazardous wastes) to the coker feedcan be desirable to achieve higher VCM increases. Embodiments, otherthan the examples, may be desirable in some cases to optimize thetechnology relative to certain constraints (e.g. causing excessive VCMcontent and/or exceeding other coker design or operational parameters).For example, the other various embodiments of the present invention arestill valid scenarios to create a premium petroleum coke with improvedfuel properties and combustion characteristics.

[0565] The results of this first process step is the production of amodified petroleum coke with a high porosity sponge coke crystallinestructure (vs. low porosity sponge coke or other crystalline forms). Inaddition, the lower severity coking operation will typically leave moreVCM in the coke, from reduced cracking reactions. Depending on the cokerfeedstocks and design parameters, the modified petroleum coke can havemodest to good adsorption qualities, and may increase VCM 3-10%. In somecases, the adsorption quality may be sufficient to justify uses intraditional activated carbon systems, with or without subsequent use asa fuel. In these cases, steam stripping the residual VCM content in theinitial phases of the quench cycle can provide sufficient activation ofthe carbon adsorption surface. In the other cases, the modifiedpetroleum coke provides a superior solid fuel that can be furtheroptimized for most solid fuel combustion applications. In addition tothe use of the premium petroleum coke of the present invention inutility boilers with pulverized coal (PC) burners, the premium petroleumcoke provides benefits in other combustion applications, as well. Othercombustion applications may include, but are not limited to (1) othersolid fuel boilers (utilities, industries, IPPs, etc.) and (2) rotarykilns in the cement and hazardous waste industries.

[0566] This first process step provides benefits to the crude oilrefinery similar to those discussed elsewhere in this application. Themajor benefits attributable to this first process step are:

[0567] 1. Reduced Heater Severity: Lower Heater Outlet Temperatures(˜50° F.-180° F. Lower)

[0568] a. Reduced Fuel Consumption: MMBtu/Hr and Btu/Lb. Feed (˜10-30+%)

[0569] b. Greater Heater Capacity; Faster Drum Fill Rate: Reduce HoursPer Cycle (˜2-6 Hours)

[0570] c. Reduced Heater Spalling, Tube Failures, Unscheduled outages, &Equipment Maintenance

[0571] 2. Reduced Fractionator Load: Higher Coke Production (Ton/MBblFeed); ˜5-10% Less Load

[0572] 3. Increased Coker Capacity: 10-40+% Increase

[0573] a. Reduced Cycle Times: 18-24 Hours Down to 12-16 Hours Per Cycle

[0574] I. Coking Cycle: Faster Drum Fill Rates

[0575] II. Quench: Eliminate “Big Steam” Strip and

[0576] III. Coke Cutting Cycle: Reduce Cutting Time (HGI >100)

[0577] 4. Improved Operation & Maintenance: Coker & Other Process Units:Less HGO; Better Quality

[0578] 5. Increased Refinery Capacity: ˜0-25% Due to Debottlenecking ofCoker Capacity Limitations

[0579] This first process step also provides benefits to the premiumpetroleum coke user. As noted earlier, this first process stepdramatically changes the petroleum coke's crystalline structure.Traditional refinery coking methods produce a petroleum coke that has adense, shot coke crystalline structure (e.g. consistency of marbles) ora shot coke/sponge coke blend with varying crystalline composition ofdensities averaging 50 to 60 lb/ft³. On the other hand, the cokermodifications of the present invention produce a less dense sponge cokewith much greater porosity. This modified crystalline structure is muchmore conducive to efficient carbon burnout levels (e.g. >99%) withoutthe need for long residence times in high temperature zones exceeding1500° F. and/or restricted to refractory lined furnaces. In addition,the very porous, sponge-coke crystalline structure gives the petroleumcoke of the present invention (1) adsorption characteristics foroptimizing fuel properties and (2) desirable capabilities as activatedcarbon in adsorption applications.

[0580] Optimization of the technology of the present invention can beused to further control coke porosity for fuel and carbon adsorptionapplications. That is, the increased coker throughput capacity(discussed above) provides the ability to introduce chemical compoundswith certain cracking and vaporization characteristics that tend toincrease the amount of voids in the petroleum coke of the presentinvention. These chemical compounds may include, but are not limited toindustrial by-products, non-hazardous wastes, or low cost products.Traditional coking processes normally cannot take advantage of thisnovel technique due to precious limits on coker feed throughput,relative to the refinery's crude throughput. In addition, these chemicalcompounds may not only increase porosity and improve carbon adsorptioncharacteristics, but also potentially provide alternative sources ofVCMs (versus loss of light ends from traditional coker feedstocks).

[0581] B. Uses of Activated Carbon Characteristics of Modified PetroleumCoke

[0582] The second major process step is the use of the modifiedpetroleum coke's activated carbon characteristics to further optimizeits fuel properties and combustion characteristics. Various processoptions have been discussed to optimize the fuel properties andcombustion characteristics of the modified petroleum coke. The potentialrole of carbon adsorption characteristics (e.g., activated carbon) inthese process options will now be discussed. Some of the fueloptimization process options may be external to the coker process (e.g.third-stage desalter). In contrast, other options may be initiated inthe coking process (i.e. in-situ). In addition, several fueloptimization process options have been added.

[0583] The first major process step produces a modified petroleum cokewith highly porous, sponge coke crystalline structure and carbonadsorption characteristics. This modified, premium petroleum cokeprovides physical and chemical properties to create the followingprocess options in the coking process. These options can furtheroptimize its fuel characteristics:

[0584] 1. Modified Crystalline Structure: Very porous, sponge cokew/HGI >100; Adsorption quality

[0585] 2. Addition of High Quality VCMs: 18-30 wt. %; Uniformlydistributed with controlled quality

[0586] 3. Ash Quality Improvement Options: Removal of troublesomemetals; Mitigate ash fusion

[0587] 4. Sulfur & Nitrogen Content Reduction Options: Various methods &degrees/incremental costs

[0588] 5. Integration of SOx Sorbents: Scavenge coke sulfur; Uniformlydistributed w/controlled quality

[0589] 6. Integration of Oxygen Compounds: Options to reduce combustionair; Uniformly distributed

[0590] 7. Optimal Use of Inherent Oxidation Catalysts: Maintain optimallevels & enhance metal catalysts

[0591] 8. Optimal Use of Carbon Adsorption Character Mercury & other airtoxics; HCs & chlorine

[0592] These reliably, controlled process options (available at variousincremental costs) allow a user to optimize the fuel properties in amanner that maximizes benefits and/or minimizes equipment andoperational modifications in the user's facilities. Hence, unlike mostother fuels (e.g. coals), the petroleum coke of the present inventioncan be consistently produced with optimal fuel properties and combustioncharacteristics. The economic and technical limits of these fueloptimization process options (and their associated incremental costs)will depend on various factors, including (1) the crude oil refinery,(2) the relative size and design of its process units, (3) the crudeblend, and (4) the coker feed blend. Discussions for each of these fueloptimization process options follow:

[0593] (1) Modified Crystalline Structure:

[0594] Most of the desired changes in coke crystalline structure can beachieved in the first major process step. However, the high internalporosity and pore volume of the modified petroleum coke allow chemicalreactions on the internal surface of the coke to further change cokecrystalline structure. For example, chemical binders may be added in tomitigate coke storage, handling, and pulverization issues, includingfriability, dust, and explosability. In most applications, these issuesare not expected to be prohibitive. In addition, the timing and methodof cutting this modified coke from the coke drum can physically alterthe coke crystalline structure.

[0595] (2) Addition of High Quality VCMS:

[0596] An exemplary process of the present invention can provide theaddition of volatile combustible materials (VCMs) in two distinct steps.The first step increases VCMs from the coker feed via operationalchanges (e.g. lower coke drum temperature) in the cracking/cokingportion of the delayed coking process (i.e. the first major processstep, described above). In the second step, VCMs are added to the cokeduring the quench cycle in a manner that uniformly distributes the VCMsthroughout premium petroleum coke's porous crystalline structure. Inboth steps, various by-products and/or wastes can be selected anduniformly integrated (e.g. mixed in coker feed in step 1) to achieve thedesired fuel properties at low costs. Alternatively, standardhydrocarbon products, such as No. 6 fuel oil, can also be used, butnormally at a higher price. Collectively, the quantity, quality, anddesired effects of how the volatile combustible materials are added totraditional coke can be controlled to reasonable specifications andconsistency. In this manner, high quality VCMs can be added uniformly tothe coke in sufficient quantity to dramatically improve flame initiationand carbon burnout.

[0597] In an exemplary embodiment, desirable VCMs (quality and quantity)can be added to the coke quench media, preferably water or other aqueoussolutions. The carbon adsorption characteristics of the modifiedpetroleum coke will provide sufficient adsorption of these VCMs(particularly non-polar VCMs) and uniformly distribute them within thecoke's internal pores. The optimal timing, temperature, and rate forVCM/quench media addition will depend on the VCMs selected and thedesired effect (e.g. VCM devolatilization in char burnout vs. combustioninitiation). Other embodiments can include post coker treatment (e.g.rail cars) to allow additional time for other options to be completed inthe coke drums during the regular coker cycle times. However, if thecycle time becomes a constraint in pursuing all of the desirable processoptions, coke drum additions may be preferable (e.g. add 3rd coke drumin cycle). Coke drum additions can provide further petroleum coketreatment time before, after, or intermediate stages of quench tomaintain desired temperatures for the specific treatment technology.

[0598] (3) Ash Quality Improvement Options:

[0599] Various process options can substantially improve combustion ashquality by reducing certain, troublesome metals in the petroleum coke.These metals can be reduced in various degrees by treatment of therefinery's crude oil blends, coker feeds, and/or the coke itself. Thepresent invention options to remove these metals of concern in all ofthese treatment methods. First, treatment of the crude oil blendstypically requires minor equipment and operational modifications to theexisting crude oil desalting system(s). Secondly, partial or fulltreatment of the coker feeds can be achieved by various methods,including hydrotreating, hydrodesulfurization, demetallization, or thirdstage desalting. The desired option will depend on the characteristicsof the refinery's crude blend, its various process units, and productslate. In many refineries, the addition of a third stage desalting unit(i.e. coker feed) can require (1) modest capital and operating costs and(2) a couple of years time to engineer and construct. All of the abovepre-coker treatments also improve the operation and product quality forother refinery process units. Thus, the incremental costs attributed tothe premium petroleum coke for these treatments may be minimal tomodest.

[0600] In an exemplary process of the present invention, the modifiedpet coke can be treated to remove metals during (in-situ) or after thecoking process (e.g. in rail cars). The high internal porosity of themodified petroleum coke and the pressurized flow of the quench mediaprovides the opportunity to chemically treat and/or remove exposedmetals of concern. Chemical products and/or by-products or wastes withchemically active components can be used to initiate and complete thedesired reactions. The resulting compound (more polar & water soluble)can be washed and removed from the modified coke. For example, spentphenolic acid from the refinery's lube oil extraction unit may be addedto the quench media for coke demetallization. This organic acid canreact with undesirable metals exposed on the internal surface of themodified coke. Residual phenolic acid will add oxygen (discussed below).The optimal timing, temperature, and rate for reactants/quench mediaaddition will depend on the metals reactive chemicals selected and thedesired effects (e.g. metals removal vs. making chemically inert).

[0601] The combination of all these metals removal methods may not berequired to achieve desired results. In fact, most applications mayrequire only one or two treatment methods, at most. The various metalremoval methods simply offer the flexibility of various options tooptimize a given refinery and achieve the same goal at the lowestpossible cost.

[0602] (4) Sulfur and Nitrogen Content Reduction Options:

[0603] Additional process changes can reduce the sulfur and nitrogencontents of the petroleum coke to various degrees with incrementalincreases in cost. As such, this modified petroleum coke can be obtainedin regular or desulfurized grades.

[0604] The sulfur content can be reduced in various degrees by (1)changing the coker feed blend, (2) partial or full treatment of thecoker feeds, and/or (3) treatment of the coke itself. Again, thetechnology of the present invention offers sulfur reduction options inthe various treatment methods, particularly for treating the coke duringor after the coking process. First, lower sulfur feeds in the coker feedblend can significantly reduce the sulfur content of the petroleum coke.Optimization of the technology (i.e. via increased coker throughputcapacity discussed above) provides the ability to introduce industrialby-products, non-hazardous wastes, or low cost products with lowersulfur content. Traditional coking processes normally cannot takeadvantage of this novel technique due to precious limits on coker feedthroughput, relative to refinery throughputs. Second, partial or fulltreatment of the coker feeds can be achieved by various methods,including hydrotreating and hydrodesulfurization. Finally, the treatmentof the petroleum coke, during or after the coking process, can take manyforms: solvent extraction, reaction with strong reducing agents, and/orhydrotreating.

[0605] In an exemplary process of the present invention, the modifiedpetroleum coke can be treated to remove sulfur and/or nitrogen during(in-situ) or after the coking process (e.g. in rail cars). The highinternal porosity of the modified petroleum coke and the pressurizedflow of the quench media provides the opportunity to chemically treatand remove exposed sulfur and/or nitrogen. Chemical products and/orby-products or wastes with chemically active components can be used toinitiate and complete the desired reactions. The resulting compound(more polar & water soluble) can be washed and removed from the modifiedcoke. For in-situ desulfurization or denitrification in the cokerprocess, the coke drums of a delayed coker may provide any one or anycombination of the following desulfurization techniques: solventextraction, reaction with strong reducing agents, hydrotreating, and/orbiodesulfurization). For example, spent phenolic acid from therefinery's lube oil extraction unit can be used as a solvent in the cokequenching cycle to extract sulfur (and nitrogen) from the petroleumcoke. This organic acid can react with sulfur (and nitrogen) exposed onthe internal surface of the modified coke. Also, strong reducing agents,such as hydroxides of calcium, magnesium, sodium, and/or potassium, canbe used in the coke quenching cycle to react with and remove sulfur fromthe coke. Hydrotreating is essentially the introduction of hydrogen athigh temperatures to saturate the hydrocarbon compounds, replacingsulfur in complex chemical structures. This treatment can be used aloneor in conjunction with other treatments to enhance their effectiveness.The use of hydrogen to increase the porosity of the modified coke(discussed above) provides intimate diffusion within the coke structure,normally the slow reaction step. The optimal timing, temperature, andrate for reactants/quench media addition will depend on the sulfurcompounds/reactive chemicals selected and the desired techniques.

[0606] In all of these desulfurization methods, the non-thiophenicsulfur (i.e. ˜20-30 wt. %) may be more easily removed. Thiophenic sulfuris not readily separated from its complex hydrocarbon compounds andgenerally requires higher temperatures (e.g. >600° F.) to break itsrelatively stable, chemical bonds. However, the cracking/coking portionof the coker process can be sufficient to convert complex, sulfurcompounds to non-thiophenic forms. Consequently, a 20-30% reductionsulfur content can be readily achieved with relatively simpleapplications of these methods. Coke treatments during or after the cokequenching cycle provide greater sulfur removal potential. Any additionalreductions of coke sulfur content can be much harder to achieve, withgreater incremental costs (i.e. more money per ton of sulfur reduced).

[0607] (5) Integration of SOx Sorbents:

[0608] The technology of the present invention anticipates the need toachieve incremental reduction of sulfur oxides in the combustion and airpollution control systems. The ability to convert the existingparticulate control device (PCD) into a sulfur oxides control is a majorfeature of the present invention. That is, the much lower ash content(>90 wt. % lower) of the petroleum coke of the present invention freesup available capacity in the existing PCD to collect sulfur oxides thatare converted to dry particulates upstream of the PCD. Methods ofinjecting various dry sorbents (e.g. limestone, hydrated lime, sodiumhydroxide, etc.) to the fuel and combustion products have beencommercially proven. However, dry sorbents mixed in with the fueltypically are less effective due to sintering of its reactivecrystalline structure in the high temperature zones of the furnace.Sorbents injected into the flue gas (at various points in the boiler orflue ducts) usually require high sorbent to sulfur molar ratios due tovarious factors. Three major factors, which prohibit the desiredchemical reactions, are:

[0609] (1) Calcination process to convert injected dry sorbent to morereactive form (e.g. CaCO₃ to CaO)

[0610] (2) Bulk diffusion of gaseous sulfur oxides to the solid sorbent,and

[0611] (3) Diffusion of sulfur oxides through sorbent pores and CaSO₄layers (e.g. blocking pores).

[0612] An exemplary process of the present invention provides processoptions for uniformly adding SOx sorbents to the modified petroleum coketo alleviate these reaction constraints. Desirable SOx sorbents (qualityand quantity) can be added to the coke quench media, preferably water orother aqueous solutions. The carbon adsorption characteristics of themodified petroleum coke will provide sufficient adsorption of thesesorbents (particularly non-polar sorbents, such as Ca(OH)2) anduniformly distribute them within the coke's internal pores. Theintegration of the sorbent in the very porous petroleum coke of thepresent invention has several advantages. First, sintering of thereactive sorbent structure is dramatically reduced, since thecalcination and crystallization of the reactive sorbent form does notoccur until after the flame's high temperature zones. That is, thesorbent (integrated in the char) does not calcine until char burnout inthe lower temperature zones of low NOx combustion modes. Secondly, thereaction limiting factors attributed to the sorbent calcination andcrystallization steps are greatly reduced. These steps occur well aheadof the SOx reaction zone of optimal temperature. Thirdly, the sorbent isintegrated in the very porous sponge crystalline structure of the coke,where most of the remaining sulfur is located. Consequently, the bulkdiffusion reaction limits (Item 2, above) are substantially reduced dueto relative close proximity of the high concentrations of SOx and highconcentrations of reactive sorbents. Finally, the very finepulverization of the highly-porous petroleum coke of the presentinvention (>90% through 200 mesh) can significantly reduce reactionlimits caused by blockage and limited diffusion to reactive pore sites(Item 3, above). The very porous structure of finer particles createsgreater reactive surface areas that are less restrictive. The optimalSOx sorbent concentration, timing, temperature, and injection rate forquench media addition will depend on the sorbents selected and thedesired impacts.

[0613] Other embodiments can include use in combination with sulfurreduction options and post-coker treatments. The use of strong reducingagents, such as calcium hydroxide, for coke desulfurization will oftenleave residual reacted sulfur compounds (not washed away) and residualcalcium sorbents. The residual calcium compounds will still be effectiveSOx sorbents: scavenging sulfur and converting to particulates forcollection by the existing particulate control device. Post cokertreatment (e.g. rail cars) can allow additional time for other optionsto be completed in the coke drums during the regular coker cycle times.However, if the cycle time becomes a constraint in pursuing all of thedesirable process options, coke drum additions may be preferable (e.g.add 3d coke drum in cycle).

[0614] (6) Options for Integration of Oxygen Compounds:

[0615] An exemplary process of the present invention provides processoptions for uniformly adding oxygen content to the modified petroleumcoke to reduce combustion air requirements. Desirable oxygen-containingcompounds (quality and quantity) can be selected and added to the cokequench media, preferably water or other aqueous solutions. The activatedcarbon characteristics of the modified petroleum coke can providesufficient adsorption of these oxygen sources (particularly non-polarchemicals, such as phenols) and uniformly distribute them within thecoke's internal pores. The type of oxygen sources can ultimately impactthe fuel's combustion characteristics. Though practically all oxygencontent of the fuel (except water) will be productive in reducingcombustion air, some types of oxygen sources can be preferable toothers. For example, oxygen compounds that are chemically bound in aheavier hydrocarbons can be more beneficial to burning the char and helpreduce excess air levels as well as theoretical combustion air levels.That is, these compounds (unlike alcohols) will not readily volatilizeat lower temperatures, and provide more effective oxidation of the charwithout higher excess air. Another example would be the injection ofphenols for desulfurization (described above), and the residual,unreacted phenols providing added oxygen content.

[0616] (7) Optimal Use of Inherent Oxidation Catalysts:

[0617] The high metals content of petroleum coke is often believed to bea problem, particularly vanadium and nickel. Options to reduce the cokemetals content can alleviate these concerns (discussed above). However,these metals can be advantageous as combustion catalysts in certainfiring modes. Catalytic oxidation can be very effective in improvingcombustion in low temperature zones with low oxygen availability,conditions often associated with low NOx combustion. Also, Vanadiumcatalysts are often used in the presence of ammonia or other reagents todecompose or oxidize nitrous oxides to molecular nitrogen and oxygen.For example, low NOx combustion firing modes have dramatically increasedthe unburned carbon of many pulverized coal boilers. This not onlysubstantially reduces boiler efficiency, but dramatically increases thecarbon content of the ash, as well. Ash carbon contents >5% can turn ashreuse sales of about $15/Ton to ash disposal costs of about $ 20/Ton. Inthis situation, catalytic oxidation caused by the metals content of thepetroleum coke of the present invention can be critical to economicviability. That is, leaving significant metals content in the petroleumcoke of the present invention can be very helpful, particularly with amodest coke portion in coal/coke blend. In addition, the catalyticoxidation can improve NOx performance, while reducing the need forsubstoichiometric combustion with severely reducing (corrosive)atmospheres that increase tube failures.

[0618] A process of the present invention recognizes the potentialbenefits to (1) maintain optimal levels of certain metals (e.g. vanadiumand nickel) and (2) enhance their oxidation catalyst characteristics.First, the optimal levels of the metals of concern can be determined foreach combustion application. Once quantified, the demetallizationprocesses, discussed above, can be adjusted to achieve the optimallevels (though possibly not independently). Secondly, the desirableoxidation catalyst characteristics can be further enhanced by chemicalor physical treatment. That is, the high internal porosity of themodified petroleum coke and the pressurized flow of the quench mediaprovides the opportunity to chemically and/or physically treat exposedoxidation catalysts. For example, chemical treatment may be used toactivate the oxidation catalyst and make it more reactive.

[0619] (8) Optimal Use of Carbon Adsorption Characteristics:

[0620] As discussed previously, the first major process step produces amodified petroleum coke with carbon adsorption characteristics (i.e.high internal porosity and pore volume). Consequently, this modifiedpetroleum coke can have the physical and chemical properties requiredfor many carbon adsorption applications (e.g., activated carbon). Theinternal and external porosities can approach and exceed 60% and 35%,respectively. The pore size can range from 5-50 angstroms. Thus, thesurface area of the petroleum coke of the present invention can approachand exceed 600 square meters per gram. These carbon adsorptioncharacteristics compare favorably with those properties for activatedcarbon form other sources. As such, the modified petroleum coke can beuseful in traditional activated carbon technologies, as well as carbonadsorption in combustion processes.

[0621] A process of the present invention can produce adsorption qualitycarbon, which can be used in traditional activated carbon technologies:water treatment, vapor recovery, adsorption of various hydrocarbons,metals and/or other toxics form gaseous or liquid streams. Theadsorption properties of this modified petroleum coke can be enhanced bysteam-stripping in the quench cycle in the carbon adsorption system orotherwise. After serving its useful life in carbon adsorption, thispremium pet coke can be further used as fuel or activated carbon incombustion processes. In either case, treatment (e.g. one finalregeneration step) may be necessary to sufficiently reduce or removeharmful contaminants (prior to combustion) to avoid undesirable airpollutants and/or ash constituents. Alternatively, this carbonadsorption coke can be further used as activated carbon in combustionprocesses.

[0622] Another process of the present invention produces modifiedpetroleum coke with adsorbent characteristics (with or without steamactivation) that can be effectively used for carbon adsorption incombustion processes. In a manner similar to steam activation, thecombustion process itself can potentially activate the unburned cokechar and promote carbon adsorption mechanisms in the flue gas. Therelative quantity of this adsorption carbon from unburned premiumpetroleum coke can be adjusted by controlling the fuel blend,pulverization fineness, excess air, and/or other parameters of thecombustion process. Alternatively, other activated carbon (e.g. seeabove paragraph) can be added to the fuel or the flue gas to providehigher concentration of activated carbon in the flue gas. In thismanner, the unburned premium petroleum coke and/or used adsorptioncarbon from the present invention can adsorb mercury, dioxins, furans,other air toxics, and other undesirable pollutants from the flue gas,including carbon dioxide, SOx, and NOx. The presence of sulfur,available in the coke, can enhance the adsorption of mercury, a growingconcern of power generation facilities. In this manner, the premium cokecan achieve further reduction of environmental emissions from thecombustion process.

[0623] 5. Additional Methods to Increase Pet coke Porosity & AdsorptionCharacter

[0624] As noted previously, various methods can be used to modify thepet coke crystalline structure, preferably to a highly porous, spongecoke. This modified crystalline structure can improve the carbonadsorption characteristics of the petroleum coke. In these cases,various chemical agents can be uniformly added to the petroleum coke inits inner voids, based on carbon adsorption technology. In this manner,the modified crystalline structure of the petroleum coke can be used invarious carbon adsorption applications and/or to further modify thecoke's fuel properties, combustion characteristics, and/or other cokequalities. Additional methods (e.g. other embodiments) are describedthat improve the pet coke's internal porosity and carbon adsorptioncharacteristics. The first two methods (i.e. coker operation/modifiedfeed and plastics/rubber addition) provide further details of similarmethods, described previously. The last three methods (i.e. cokehydroprocessing, coke extraction, and coke chemical activation) areadditional embodiments that can achieve the intent and needs of thecurrent invention.

[0625] It should also be noted that all of these methods could be usedfor purposes other than increasing pet coke porosity and enhancingadsorption characteristics. That is, these methods have additionalbenefits (e.g. wastes recycling) and can be used independent of theirability to increase coke porosity and improve pet coke adsorptioncharacteristics. Thus, the present invention is not limited to their useto increase porosity, but also includes these methods for otherpurposes.

[0626] A. Carbon Adsorption Characteristics

[0627] Various porous materials demonstrate some degree of adsorptioncharacter. The internal pore structures of these solid materials(adsorbents) provide an internal surface where various chemicalcompounds (adsorbates) in a passing fluid can be held by Van der Waalsand/or other molecular forces. In general, good adsorption character isdefined by various measured parameters related to the internal porestructure of the adsorbent. These parameters provide relativecomparisons that help screen potential adsorbents. However, theselection of the desired adsorbent depends on other factors associatedwith the adsorbate system characteristics. These selection processesusually involve case-by-case analyses.

[0628] The shapes and sizes of pores are an important factor in carbonadsorption technology. Pores are typically classified into threedifferent size categories (as defined by IUPAC): micropores, mesopores,and macropores. Micropores have a diameter of <2 nm (nanometers).Mesopores have diameters between 2 and 50 nm. Macropores havediameters >50 nm. Micropores and mesopores primarily give porous carbonmaterials their adsorption capacities. These types of pores are oftenformed during the process of activation. Activation is basically furtherdevelopment of pores in low porous raw material by chemical reactions.Traditionally, ‘physical’ activation (i.e. oxidation with gases: steam,carbon dioxide, or air) and chemical activation (i.e. reaction withchemical agents prior to heat treatment) are two processes that givefundamentally different pore structures.

[0629] Various measured parameters of pore structure provide relativeindications of adsorption performance. Three of the most commonadsorption parameters are (1) internal porosity, (2) pore sizedistribution, and (3) internal surface area. Carbonaceous materials withvery high porosity and large surface areas generally provide goodadsorption qualities. Activated carbons are highly porous, carbonaceousmaterials that provide exceptional adsorption capabilities. One of themost widely used parameters to measure the effectiveness of pores inactivated carbons is the total surface area or BET surface area. BETsurface area uses a projection model and adsorption data to account formulti-layer adsorption effects. Most of the total surface area is foundin the micropores. Typical data 2 for an activated carbon are: >500square meters per gram (m Ig) in micropores, 10 to 100 m²g in mesopores,and <10 m²/g in macropores.

[0630] These adsorption parameters are useful for general comparison ofpotential adsorption character among adsorbents and provide preliminaryindication of relative adsorption performance. However, the desiredadsorbent for a particular application depends on (1) thephysical/chemical characteristics of the adsorbate, (2) thephysical/chemical characteristics of the fluid system containing theadsorbate, and (3) concentration of the adsorbate in the fluid system.Consequently, the desired adsorbent is normally determined on acase-by-case basis. In many applications, only part of the total surfacearea is accessible for the molecules to be adsorbed. In these cases,molecules, which are to be adsorbed, are too large to fit into themicropores. For example, most liquid-phase applications require theadsorption of high molecular weight materials. Most of these largercompounds, by their size, are excluded from a large part of themicropore system. As such, a carbon with high number of mesopores isrequired, and a carbon with high total surface area of predominantlymicropores provides no value. Ideally, the carbon should have a largenumber of pores, which are just slightly larger than the size of themolecules to be adsorbed. Smaller pores are inaccessible, and muchlarger pores provide relatively little surface area per unit volume.Consequently, the activated carbon industry characterizes their carbonsby adsorption properties rather than pore structures.

[0631] In conclusion, carbon adsorption character is more of an art thanscience. Adsorption characteristics can vary considerably and are notabsolute in terms of measured adsorption parameters. As such, it isdifficult to specifically define adsorption character by specific rangesof analytical measurements of adsorption parameters. Instead, adsorptioncharacter is more appropriately dealt with on a case-by-case basis. Thatis, the best carbon adsorption character is highly dependent on thespecific adsorbate(s) and conditions of a particular adsorptionapplication. Therefore, the ranges of specifications for desired carbonadsorption character are provided as a guide for most situations.However, variance outside of these ranges can occur in some cases due to(1) coker feedstocks and operations, (2) characteristics of targetedadsorbate(s), (3) physical and chemical conditions of adsorption, and/or(4) other factors. Thus, the present invention is not limited to thesespecific ranges, but also includes variance from these ranges, whereinthe spirit of the present invention and its advantages are maintained.

[0632] B. Improved Carbon Adsorption Character: Modified Operationand/or Feed

[0633] The porosity and adsorption characteristics of petroleum coke canvary substantially due to variations in the coker feedstocks, design,and operating conditions. As discussed previously, there are three basictypes of pet coke crystalline structures from a delayed coking process:shot, sponge, and needle. These basic coke crystalline structures havesubstantially different porosity and adsorption characteristics. Theporosity and adsorption character within these crystallineclassifications and their associated transition zones can also varyconsiderably.

[0634] The shapes and sizes of the pores in the petroleum coke can playa major role in its carbon adsorption characteristics and capacities.Adsorption qualities of traditional activated carbons may not benecessary for pet coke fuel enhancements. However, pet coke withadsorption characteristics approaching this level can be desirable forfuel enhancements and/or other adsorption applications, if economicallypractical.

[0635] (1) Petroleum Coke Crystalline Growth:

[0636] Modifications of the pet coke crystalline structure have beenpreviously discussed. The effects of coker design, feedstocks, andoperating conditions were described relative to two coking mechanisms:asphaltic and thermal coking. The resulting three types of cokecrystalline structure (shot, sponge, and needle) were also discussed.However, further discussion of the coker crystalline growth isappropriate to describe the pet coke's carbon adsorptioncharacteristics. In these complex chemical structures, there is muchdebate about how and when the pet coke crystals form. It is not clearwhen the formation of the chemical bonds of petroleum coke ends and theformation of pet coke crystals begins. In general, both cokingmechanisms and pet coke crystal growth occur sequentially in the cokingand decoking cycles of the delayed coking process. The following theoryof coke formation and crystalline growth is presented as a basis forunderstanding the methods described previously. However, the presentinvention should not be bound or limited by this theory of operability.

[0637] In the formation of shot coke, the asphaltic coking mechanism ispredominant. In this case, the coker's cracking reactions causeconversions that shift the solvent properties of the oil mixture (e.g.the loss of aliphatic and napthenic chains), and disrupt the colloidalsuspension of the asphaltenes and resins. As a result, the asphaltenesand resins are precipitated in a manner that forms a highly cross-linkedstructure of amorphous coke. This desolutation is primarily physicalchanges with limited alteration of chemical bonds (mostly cross-linkingbetween asphaltenes, resins, and some aromatic compounds). Theprecipitated coke tends to form imperfect spherical balls, ranging insize from <0.25 inches to >10 inches. This amorphous coke crystallinestructure is commonly called shot coke. At the higher temperatures ofthe coking cycle, the shot coke tends to remain in a two-phase,solid/liquid residue. The pressurized liquid/gas coker feed and thevapors from the cracking reactions flow upward through this coke mass.However, the shot coke structure is very dense, and does not allow thepenetration or permeation by these gases. As such, these gases flowaround the shot coke (e.g. channeling). Similarly, in the decokingcycle, the stripping steam and cooling media pass between the balls ofshot coke. Consequently, shot coke maintains a very dense, amorphouscoke structure with limited porosity, even after the cooling of thedecoking cycle. Shot coke tends to have high impurities concentrationsand high C/H ratios. Typically, this amorphous coke is undesirable foranode manufacture and coker operations (e.g. blockage of drainage indecoking cycle & safety).

[0638] In the formation of needle coke, the thermal coking mechanism isvery predominant, with little to no asphaltic coking mechanismoccurring. In this case, coke is typically made from highly aromaticcoker feedstocks (e.g. thermal tars or decanted oils). As such, theconcentration of asphaltenes and resins in the coker feed is very low.The thermal coking mechanisms cause the condensation and polymerizationof the heavy hydrocarbons (mostly aromatics). Without the asphaltenes,resins, and their associated impurities, this needle coke crystallinestructure is uniform, tightly packed, and rigid. In the coking cycle,the needle coke crystalline structure is initiated, but tends to remainin a two-phase, solid/liquid residue due to the higher temperatures. Thepressurized coker feed liquid and cracked gases flow upward throughchannels between crystalline matrices in the semi-solid coke mass. Inthe decoking cycle, the thermal coking mechanism continues to a limitedextent. The stripping steam and cooling media pass through matrixchannels in the solidifying coke mass. By the end of the decoking cycle,the needle coke is normally cooled sufficiently to form a verycrystalline solid that can be cut and extracted from the coke drums.Ultimately, the needle coke has numerous unidirectional pores that arevery slender, elliptical, and largely interconnected. The thick cokewalls surrounding the voids are fragile, and form needle-shaped pieces,when broken.

[0639] The formation of sponge coke can be described as an intermediatecoke classification between shot and needle coke. The thermal cokingmechanism is predominant, but the asphaltic coking mechanism occurs, aswell. In this case, the ratio R (i.e. asphaltic coke to thermal coke) issufficiently low, and the asphaltenes and resins mostly remain insolution. The thermal coking mechanism causes condensation andpolymerization of the heavy hydrocarbons (e.g. aromatics), and somecross-linking to asphaltenes and resins. In this manner, the asphaltenesand resins are integrated in a complex coke crystalline structure, andapparently behave like impurities in the crystallization of a purecompound. That is, the polymerization and cross-linking of the heavyaromatics with the asphaltenes and resins tend to form a non-symmetric(i.e. less uniform) and flexible (less rigid) crystalline structure. Inthe coking cycle, the formation of sponge coke is initiated, though itstill remains semi-solid at these higher temperatures. The pressurizedcoker feed liquid and gas vapors from the cracking reactions penetratethis crystalline structure as they flow upward through the coke mass,initiating the development of pores of various sizes. In the decokingcycle, the thermal coking mechanism continues to a limited extent. Asthe stripping steam passes through the semi-solid coke mass, more poresare created in the sponge coke. Additional pores are created in thesponge coke, as the cooling media (water and/or low pressure/temperaturesteam) pass through the solidifying coke mass. By the end of thedecoking cycle, the sponge coke is normally cooled sufficiently to asolid form for cutting and extraction from the coke drums. Ultimately,the sponge coke has numerous pores that are random with limitedinterconnectedness. The coke walls vary in thickness. Even so, thesponge coke has significant porosity and carbon adsorption character, asevidenced by the removal of cracked liquids from the pet coke in thedecoking cycle release via steam stripping. During calcination, lighterhydrocarbons have also been released at higher temperatures, even aftersteam stripping.

[0640] Transitions between these three types of coke crystallinestructure are not clear-cut. That is, certain ranges of the ratio R(i.e. asphaltic coke to thermal coke) represent the transition zonesbetween these crystalline structures. In these transitions zones, theoverall pet coke qualities can be a hybrid (or intermediate)characteristics of the two basic cokes. For example, a pet coke in thetransition zone between sponge coke and needle coke can take onproperties of each or intermediate qualities. This transition coke canbe a higher porosity, sponge coke with elliptical, unidirectional poresthat are interconnected and highly permeable. This intermediate coke hascrystals similar to honeycomb. On the other hand, localized phenomenonin these transition zones can override these general rules, and acombination of the two coke crystalline structures can form in the samecoke drum. For example, a combination of shot coke and sponge coke canbe produced. Likewise, a combination of sponge coke and needle coke canbe produced.

[0641] As noted previously, these transition zones (or crossover points)between shot, sponge, and needle cokes are not well defined and areexpected to vary with coker feedstocks. That is, the ratio R (asphalticcoke to thermal coke) is difficult to measure. For a given coker feed,ratio R can vary for different coker designs and operating conditions.Consequently, pilot plant data are usually desirable to determine thetypes of cokes and transitions zones derived from specific coker design,operating conditions, and coker feedstocks. This can be readilyaccomplished by one skilled in the art of delayed coking. Typicalengineering methods can then be employed by one skilled in the art toachieve the methods described in the following sections.

[0642] The internal porosity of petroleum coke varies substantially.Shot coke, as its name implies, has the consistency of buck shot withvery limited internal porosity (typically <10%). On the other hand,sponge coke, as its name implies, has the consistency of sponge orvolcanic pumice with significantly greater internal porosity. Theinternal porosity of sponge coke can range from 15%-60+%, depending oncoker feedstock characteristics, coker operating conditions, and cokeVCM content. Traditional sponge coke with 8-12 wt. % VCM is on the lowerend of this range. The modified coke of the current invention (13-25 wt.% VCM) usually has internal porosity on the upper end of this range. Theinternal porosity of froth coke from the coke/foam interface can be ashigh as 90%. In contrast, the internal porosity of activated carbonsvaries significantly between 30 and 85%, depending on the carbon source,carbonization process, and activation process. The internal porosity ofpetroleum coke normally achieves a maximum value when the asphaltic tothermal coking is sufficiently low to initiate the transition fromsponge coke to needle coke. In this transition zone, honeycomb cokemaintains a high internal porosity, but the distribution of pore sizecan favor larger pores and thus, undesirable for some adsorptionapplications. As the crystalline structure approaches needle coke, theinternal porosity decreases to roughly 10-20%.

[0643] Distribution of pore sizes also varies considerably among thedifferent types of pet coke crystalline structures. In shot coke, accessto the very limited internal porosity is greatly inhibited byinsufficient pores on the external surface, regardless of pore sizedistribution. The pore size distribution of traditional sponge coketends to be predominantly macropores. However, the modified sponge cokeof the current invention tends to have higher percentages of mesoporesand micropores, particularly near the honeycomb coke transition zone. Incontrast, the pore size distribution for commercial activated carbonsvaries considerably depending on carbon source, carbonization process,and activation process. For example, bituminous coals with steamactivation typically have roughly equal distribution of micropores,mesopores, and macropores.

[0644] (2) Improvement of Pet Coke Carbon Adsorption Character:

[0645] Various methods to modify the coke crystalline structure havebeen presented that can promote greater carbon adsorption qualities. Ithas been further discovered that certain coker operations can producecertain types of coke crystalline structure that have more optimal petcoke adsorption characteristics. In addition, it has been discoveredthat the pore size and quantity can be controlled, to a limited degree,to improve the carbon adsorption characteristics of the sponge cokecrystalline structure.

[0646] a. Optimal Pet Coke Crystalline Structure:

[0647] Various coker process modifications can be used to produce petcoke crystalline structures that have more optimal carbon adsorptioncharacteristics. The theory relating coke crystalline structure to thecoking mechanism ratio R (asphaltic coke/thermal coke) can be useful todemonstrate this principle. For a given coker feed, certain ranges ofthe coking mechanism ratio can be achieved that produce pet cokecrystalline structure with desired porosity and better carbon adsorptioncharacteristics. Theoretically, a specific coking mechanism ratio arecan be maintained for a given feed, and produce the type of pet cokecrystalline structure that maximizes carbon adsorption characteristics(e.g. maximum micropores). For many coker feeds, this specific cokingmechanism ratio R would fall in the transition zones between sponge cokeand needle coke (e.g. honeycomb coke). However, due to economicconstraints, the coking mechanism ratio can be preferably controlled toproduce a sponge coke that has sufficient adsorption characteristics,but less than this maximum. This optimal level of carbon adsorptioncharacteristics (previously described as higher porosity, sponge coke)will depend on various factors including, but not limited to, (1) sizeof materials to be adsorbed, (2) pet coke use & value, and (3) loss &value of alternative coker products. In this manner, the coke mechanismratio can be theoretically used to control the porosity of the spongecoke, and its inherent carbon adsorption characteristics.

[0648] In practical applications of this theory, the actual measurementand determination of the optimal coke mechanism ratio R (asphalticcoke/thermal coke) are not necessary. As noted previously, a specificrecipe for all refineries is impractical due to the nature of thedelayed coking process and the major differences in coker feedstocks andprocess requirements among various refineries. However, one skilled inthe art of delayed coking can determine the coker conditions required toachieve the pet coke crystalline structure with the optimal carbonadsorption characteristics. Coker pilot plant studies can empiricallydetermine the required coker conditions without undue experimentation.This is standard practice in the refining industry. The determination ofthe optimal pet coke crystalline structure will require measurement ofthe carbon adsorption characteristics relative to the materials to beadsorbed. Also, effects on coker product yields and their impact onrefinery profitability (LP models) will need to be taken into account ona case-by-case basis. Initially, the baseline must be established for aspecific refinery's current operations. Incremental deviations from thisbaseline can be established for applicable operating parameters. In mostcases, the basic understanding of feedstock characteristics and cokeroperating conditions that affect the coking mechanism ratio (asphalticcoke/thermal coke) should provide the foundation to fine tune cokerconditions. As noted previously, the thermal coking mechanism isprimarily dependent on the coker operating conditions, but alsodependent on the aromatics concentration of the coker feedstocks. On theother hand, the asphaltic coking mechanism is primarily dependent oncoker feedstock quality, and limited dependence on coker operatingconditions. In this regard, the impacts of certain coker operatingconditions and coker feedstock modifications are discussed further.

[0649] Certain coker operating conditions primarily affect the thermalcoking mechanism, but have indirect effects on the asphaltic cokingmechanism, as well. Modifications to coker operating conditions werepreviously discussed that modified the coke crystalline structure. Mostof these coker modifications essentially favored the thermal cokingmechanism, and decreased the coking mechanism ratio R (asphalticcoking/thermal coking). According to the theory of coking mechanismratio, the previously prescribed modifications achieved a cokingmechanism ratio that was primarily sponge coke, and preferably higherporosity, sponge coke (consistent with the theory's transition zonebetween sponge coke and needle coke). The concept of an optimal cokingmechanism ratio is also consistent with achieving sufficient carbonadsorption to modify fuel properties, while maintaining favorable cokereconomics. The coker operating conditions of primary concern are (1)heater outlet temperature, (2) coke drum pressure, and (3) recycle rate.The direct and indirect effects of these coker operating conditions weredescribed previously. The reductions in the heater outlet temperaturereduced both endothermic coking and cracking reactions. However, itsassociated reduction in cracking reactions and drum temperature tend toincrease the aromatic content in the drum. That is, the cracking ofheavy aromatics is normally reduced first by lower temperatures. In mostcases, low to moderate changes in heater outlet temperature has theoverall effect of increasing thermal coking mechanism. In contrast,higher coke drum pressure and recycle rates tend to increase the thermalcoking mechanism simply by increasing the aromatics concentration in thecoke drum. These coker operation variables also indirectly affect theasphaltic coking mechanism to the extent that (1) they decreasearomatics content in the coke drum and/or (2) they increase the crackingreactions that destabilize the solvent properties of the oil mixtures.The effects of these operating variables are discussed previously ingreater detail. In addition, the coking cycle quench of the vaporcracking reactions (the new independent coker operating variable alsodiscussed earlier in the first section) can also affect the thermalcoking mechanism by keeping more aromatics in the coke drum. Inconclusion, the previously prescribed modifications to the cokeroperating conditions can be used to achieve the optimal coking mechanismratio for given coker feedstock in a specific refinery. In this manner,the optimal coke crystalline structure for sufficient carbon adsorptioncharacteristics can be maintained for desired use(s) and process optionsof the current invention.

[0650] Modifications to the coker feedstock can also be used to promotethe desired carbon adsorption characteristics in the pet coke. Theaddition of oils (0.1-99 wt. %; preferably 10 to 50 wt. %) with highconcentrations of aromatics (30-100 wt. %; preferably >50 wt. %) and lowlevels of asphaltenes & resins (0.1-15 wt. %; preferably <5 wt. %) cansignificantly decrease the coking mechanism ratio, and promote a higherporosity, sponge coke. For example, aromatic crudes, thermal tars, andcoal tars can be added to the coker feedstock. This would enhance thethermal coking mechanism and decrease the coking mechanism ratio. Inturn, this would likely increase the porosity of the pet coke andenhance its carbon adsorption characteristics. Likewise, FCCU slurryoils/decanted oils could be used in a similar manner. However, theamount of these highly aromatic FCCU oils recycled to the coker can becontrolled by coker operations via reducing heavy aromatics in the cokergas oils. In this manner, the FCCU slurry oils/decanted oils can beproductively used to upgrade all of the pet coke to higher quality andvalue. In contrast, small cokers, dedicated to the production of needlecoke, have upgraded just these highly aromatic feedstocks alone.

[0651] In conclusion, the optimal crystalline structure of the base petcoke can very considerably and depends on many factors, which includebut should not be limited to the following:

[0652] 1. Coker design, operation, & feedstocks: Varies form refinery torefinery

[0653] 2. Pet coke end-use: Fuel and/or carbon adsorption applications;

[0654] Varies with application

[0655] 3. Additional Coke Treatment: Additional pore development and petcoke additives

[0656] As such, the adsorption characteristics of the optimal pet cokecrystalline structure can vary greatly. The internal porosity of theoptimal coke crystalline structure is expected to be in the range of 30to 85 wt. %, preferably 50 to 65 wt. %. The pore size distribution ofthe optimal pet coke crystalline structure may be roughly equaldistribution of macropores, mesopores, and micropores. In manyapplications, a higher distribution of micropores and mesopores ispreferable (e.g. 50% micropores, 30% mesopores, and 20% macropores).However, greater distribution of macropores (e.g. 70% macropores, 20%micropores, and 10% mesopores) can be acceptable for carbon adsorptionof some chemical agents for fuel enhancements. The internal surface areaof the optimal pet coke crystalline structures can vary considerably.However, the optimal pet coke crystalline structure is expected toprovide surface area of 100 to 1000 square meters per gram; preferably600 to 1000 square meters per gram. In general, an exemplary pet cokecrystalline structure has greater volumes of mesopores and microporesthan traditional sponge coke. In many applications, the anisotropicmicrostructure of the honeycomb coke can be preferable due to its poreinterconnectedness and lower pressure drop capability. In otherapplications, the isotropic microstructure of highly, porous sponge coke(immediately prior to the honeycomb coke transition zone) can bepreferable due to less graphitizable nature and higher volumes ofmicropores. In still other applications, a hybrid microstructure ofthese two in the transition zone can be preferable for optimal qualitiesof both. In still other applications, a porous coke structure with thickwalls and small pores (sometimes called dense sponge vs. porous sponge)can be preferable due to its higher density and distribution ofmicropores.

[0657] An optimal coke crystalline structure may not only increaseporosity and carbon adsorption character, but can also increase itssusceptibility for further development of pore structure (e.g.activation). With the exception of needle coke, the lowering of thecoking mechanism ratio R (via changes in process conditions and/or cokerfeed changes) usually modifies the coke crystalline structure in amanner that increases crystal imperfections and/or changes thermoplasticcharacter of the coke. In fuel-grade, sponge coke, high sulfur and highmetals content already act as impurities in the crystalline structure,creating an isotropic structure with numerous pores due to its imperfectcrystals. The addition of more VCMs (i.e. higher hydrogen content and/orlower carbon to hydrogen ratio) in the current invention furtherincreases the degrees of crystal imperfections and associated porosity.These properties already make it less desirable as a graphitizablecarbon, and hence its fuel-grade classification. These imperfections inthe crystalline structure present more reactive sites for activation.For example, the additional VCMs and their associated hydrogen make thepet coke less graphitizable and more susceptible to hydrogenationreactions (i.e. reversible dehydrogenation reactions). In addition, thecross-linking of the VCMs into the crystalline structure can alsosignificantly change the pet coke's thermoplastic character towardthermosetting character. In this manner, the pet coke behaves more likea char that doesn't go through a plastic stage with associatedrealignment of crystallites and loss of porosity at high temperatures.Similarly, the anode-grade, sponge coke can be altered via cross-linkingof VCMs into the coke crystalline structure. However, the crystallineimperfections and the reduction of thermoplastic character are not aspronounced due to the lower sulfur and metals contents. With eitherhigh-porosity, sponge coke, these modified characteristics make themodified coke of the current invention more susceptible to furtherdevelopment of pore structure via activation by traditional andnon-traditional methods.

[0658] b. Physical/Chemical Influences on Pore Development.

[0659] If the pet coke crystalline structure is sponge coke orsufficiently close to sponge coke (i.e. vs. shot coke), certain chemicalcompounds can be added to the coker process and increase the pet cokeporosity. These chemical agents EITHER are low molecular weight (MW)gases OR release low MW gases/vapors at the coke drum operatingconditions (e.g. cracking reactions). The low MW gases/vapors wouldinclude, but should not be limited to, H₂, H₂O, NH₃, CH₄, NO, CO, C₂H₆,CO₂, NO₂, C₃H₈. These low MW gases/vapors can physically and/orchemically influence the development of pores in the solidifying cokemass during crystal growth. That is, the low MW gases/vapors passingupward through the solidifying coke mass affect the number, shapes, andsizes of the pores in the pet coke. Overall, these additional low MWgases tend to increase the quantity of micropores. Similarly, additionalhigher molecular weight, hydrocarbon vapors can generally increase thedegree of mesopores, as well. In addition, the injected chemicalcompounds can physically or chemically alter crystal growth. Theincreased microporosity and total surface area improves the adsorptionqualities of the pet coke, particularly for many gaseous adsorptionapplications. The increased mesoporosity improves the adsorptionqualities of the pet coke, particularly for many liquid media adsorptionapplications. Furthermore, these injected chemical compounds caninfluence the chemical nature of the carbon surfaces, which effect itsadsorption and chemisorption character. For example, oxygen, nitrogen,and halogen compounds can significantly alter the adsorption carboncharacter via the formation of surface groups and/or complexes. Thus,the addition of these chemical compounds can substantially modify andincrease the carbon adsorption characteristics of the petroleum coke.

[0660] Various methods to introduce such chemical compounds weredescribed earlier. The primary purposes of adding these materials to thecoker feedstocks are to (1) enhance carbon adsorption characteristics ofthe petroleum coke, (2) enhance coker product yields, and/or (3) providerecycling of these waste materials without the need to sort by wastetype, particularly plastics. The following methods are described withgreater specificity regarding (1) injection methods, (2) control of porenumber, sizes, & shapes, and (3) impacts on the coking/crackingreactions.

[0661] b1. Addition of Oxygen-Containing, Carbonaceous Compounds:

[0662] Promote Sponge Coke (vs. Shot): The addition of oxygen-containingcarbonaceous compounds (i.e. 5-60 wt. % oxygen) to the coker wasdiscussed previously. This unique application to the delayed coker (1)produces high porosity, sponge coke (vs. shot coke), (2) enhances petcoke adsorption characteristics to improve fuel properties & combustioncharacteristics, and (3) modifies pet coke for fuel use. The key aspectof this method was the production of low molecular weight gases thatcontained oxygen (e.g. H₂O, CO, CO₂, CH₄OH) from the cracking of theadded compounds under the coke drum operating conditions. Theseoxygen-containing, carbonaceous compounds would include, but should notbe limited to, coals, coal wastes, wood, wood wastes, paper, andcardboard. In general, these chemical agents are pulverized to less than50 mesh and added (e.g. pressurized feed slurry) to the coker feed,preferably the recycle stream before the fractionator, and/or mostpreferably in the combined stream after the fractionator. The quantityof chemical agents to achieve the desired effects can range from 0.1-20wt. %; preferably 5-10 wt. %.

[0663] b2. Injection of Other Chemical Agents: Cracking Release of LowMW Gases:

[0664] The current invention also described methods to add otherchemical compounds (including carbonaceous materials without oxygen) tothe delayed coking process that would achieve similar effects. Thesechemical compounds were either low-molecular weight gases or chemicalcompounds that released low MW gases/vapors into the coke mass. Thelow-molecular weight gases can be added to the bottom of the coke drumduring the coking cycle (if inert in the cracking process) or at thestart of the decoking cycle. The primary examples of these compounds arehydrogen gas (in the decoking cycle) and various plastics. In a similarmanner, rubber compounds (e.g. scrap rubber) can be added to accomplishthese objectives, as well. In general, these chemical agents arepulverized to less than 50 mesh and added (e.g. pressurized feed slurry)to the coker feed, preferably the recycle stream before thefractionator, and/or most preferably in the combined stream after thefractionator. The quantity of chemical agents to achieve the desiredeffects can range from 0.1-20 wt. %; preferably 5-10 wt. %. Though analternative injection of plastics was described earlier, anotherexemplary embodiment for plastics/rubber injection is presented below.

[0665] b3. Direct Injection of Hydrogen or Fuel Gas into the Coke Massafter the Coking Cycle:

[0666] Direct injection of hydrogen or refinery fuel gas into the cokemass after the coking cycle can greatly enhance the pet coke's carbonadsorption characteristics. Though hydrogen may be preferred due to itseffectiveness, refinery fuel gas (e.g. coker off-gas), particularly withhigh hydrogen content, can achieve the desired results with less impacton the fractionator load limits (i.e. lb-mol/hr.) Hydrogen gas or fuelgas injection into the coke mass during the coking cycle can prematurelyquench the cracking and coking reactions in the coke drum and defeat thepurpose of the delayed coking process. However, injection of pressurizedhydrogen gas or fuel gas into the solidifying coke mass after the cokingcycle can greatly increase the quantity of mesopores and preferablymicropores in the sponge coke. In addition, hydrogenation of variousreactive hydrocarbons in the modified coke can occur to a limiteddegree. This hydrogenation step can produce additional cracked liquidsand increase porosity. In general, hydrogen (of various purities) can beinjected (e.g. with steam) into the bottom of the drum after the feedhas been transferred to the other coke drum. The quantity of chemicalagents to achieve the desired effects can range from 0.1-20 wt. %;preferably 1-5 wt. %.

[0667] C. Plastics/Rubber Addition to Coker: Exemplary Embodiment

[0668] Previously, methods were described to add plastics, paper,cardboard, wood wastes, and/or various other carbonaceous materials tothe delayed coking process. The primary purposes of adding thesematerials to the coker feedstocks are to (1) enhance coker productyields, (2) enhance carbon adsorption characteristics of the petroleumcoke, and/or (3) provide recycling of these waste materials without theneed to sort by waste type, particularly plastics and rubber compounds.An exemplary embodiment for the injection of plastics/rubber has beenfurther discovered, and discussed below. In addition, rubber productsthat have similar characteristics (i.e. desirable for the currentinvention) can also be recycled as coker feedstock (with or withoutother plastics). The addition of certain quantities of othercarbonaceous materials (separately or in combination) in a similarmanner can also be advantageous.

[0669] (1) Unique Use of Extruder/Injection Technologies:

[0670] An exemplary embodiment for the injection of plastics and/orrubber compounds into the delayed coking process includes a unique useof extruder and/or injection molding technologies. The primary purposesof this unique application of extruder technology are to (1) pulverizemixed plastics/rubber to a uniform size distribution, (2) gradually meltthe plastics/rubber to prevent coking or excess vaporization, and (3)inject the melted plastic at high pressures and optimal temperatures tominimize vaporization and provide the motive force to properly injectthe plastics/rubber into the coker feedstocks.

[0671] First, an appropriate pulverizer must be selected to pulverizevarious plastics/rubber of various shapes and sizes to pellet size orsmaller (2 to 100 mesh; preferably 50 to 100 mesh), depending onextruder feed specification requirements. A conventional or commerciallyavailable vortex shredder and/or soft solids pulverizer with sizeclassifiers can provide adequate pulverization. However, the chosenpulverization system must address concerns of high temperatures andpotential plugging. One skilled in the art of solids handling andpulverization can select (or design) the pulverization system(s) toachieve these objectives.

[0672] Next, the proper extruder/injection system must be selected (andmodified) or engineered to (1) gradually heat & melt theplastics/rubber, (2) pressurize the molten plastics/rubber, and (3)inject into the delayed coker, similar to rubber extrusion. Multipleextruders may be necessary to achieve the flow rate required for a givencoker application. Gradually heating the plastics/rubber at controlledtemperatures in a pressurized system is critical to prevent coking andlimit vaporization. Preferably, the controlled temperature increasesshould not exceed 10 degrees Centigrade per minute. The maximumtemperature at injection should be significantly below (5-30° F.;preferably 10-20° F.) (1) the coking temperatures of the plastics/rubberof concern, and/or (2) vaporization temperatures of >80% of theplastics/rubber, preferably >90%. The pressure of the extruder willdepend on various factors, including (but not limited to) flow rateconsiderations, vaporization characteristics of the plastics/rubber, andpressure requirements of the delayed coker injection point. Thetemperature of the plastics/rubber at the point of injection may besignificantly less than the temperature of the coker feedstock.Consequently, the heater outlet temperature must be adjusted to achievethe desired drum temperature after the plastics/rubber are added.Depending on coker process requirements and the quantities andproperties of the plastics/rubber, one skilled in the art can make theappropriate modifications for each application via engineeringcalculations and minor tests, if necessary. In general, the variousplastics and/or rubber compounds are pulverized and added to theextruder injection system. The molten plastics/rubber compounds areinjected into the coker feed, the recycle stream before thefractionator, and/or most preferably in the combined stream after thefractionator. The quantity of recycled plastics and/or rubber compoundsto achieve the desired effects can range from 0.1-30 wt. %; preferably5-15 wt. %. Conceivably, other pulverized carbonaceous materials couldbe added to the extruder/injection system (e.g. plastics/paper slurry).However, the quantity of these materials would limited by the extruderinjector design.

[0673] D. Coke Hydroprocessinq in Coke Drums

[0674] As previously discussed, various coker process modifications canalter pet coke crystalline structure, preferably sponge coke with higherporosity and improved carbon adsorption characteristics. Additionalcoker process modifications have been discovered to improve pet cokeproperties via low-severity, hydroprocessing of the petroleum coke.

[0675] (1) Prior Art: Hydroprocessing of Petroleum Products:

[0676] Hydrogenation, one of the oldest catalytic processes, is theprimary component of a group of various petroleum upgrading processes,generally called hydroprocessing. Hydrocracking is a type ofhydroprocessing that combines hydrogenation with catalytic cracking.Hydrotreating is another class of hydroprocessing technologies thatselectively treat and remove certain impurities via catalytichydrogenation. Hydroprocessing technologies for residuals typically usecatalytic hydrogenation to remove impurities (similar to hydrotreating)followed by the combination of catalytic hydrogenation and catalyticcracking (similar to hydrocracking).

[0677] a. Prior Art; Hydrocracking of Gas Oils & Middle Distillates:

[0678] The hydrocracking process was originally developed for upgradingpetroleum feedstocks in the early 1930s. Hydrocracking combinescatalytic cracking (e.g. scission of carbon-carbon single bonds) withcatalytic hydrogenation (e.g. hydrogen addition to carbon-carbon doublebonds). In this process, complementary reaction mechanisms occur;endothermic cracking provides olefins and aromatics for hydrogenation,while exothermic hydrogenation provides excess heat for cracking andtemperature increases, if desirable.

[0679] Most hydrocracking catalysts normally consist of silica-aluminabase impregnated with a rare earth metal (e.g. platinum, palladium, &nickel). The silica-alumina promotes cracking activity, while the rareearth promotes hydrogenation. Typically, the catalyst is selective withrespect to less production of propane and lighter versus normal crackingprocesses. This catalyst selectivity reduces with age, producing moregas at the end of run, requiring higher temperatures to maintainconversion. The catalyst activity also decreases over time with theaccumulation of coke and other deposits, requiring regeneration abovecertain threshold levels. The circulation of large quantities ofhydrogen with the feedstock usually inhibits catalyst fouling. Inaddition, hydrocracking catalysts are susceptible to poisoning bymetallic salts, oxygen, organic nitrogen and sulfur in the feedstocks.Consequently, the feedstocks are often hydrotreated either internally(i.e. guard reactor) or externally (see hydrotreating below) to removesulfur, nitrogen, oxygen, and metals, while saturating feedstockolefins. Compositions of hydrocracking catalysts are normally tailoredto the process, feeds, and desired products.

[0680] The hydrocracking process is typically a fixed-bed, regenerativeprocess, with one or two stages of reactors. Each reactor normally hasseveral beds of catalyst to allow injection of cold, recycled hydrogenfor temperature control. Hydrogen-rich gas is usually mixed with thefeed prior to the feed heater. The two-phase fluid from the heateroutlet typically flows downward through the reactors. The hydrogen-richgas in the reactor effluent is separated form the oil products andrecycled with hydrogen makeup to be mixed with feed at the heater inlet.Operating conditions in the reactor(s) range from 500 to 800 OF and 1000to 2000 psig. The temperature and pressure vary with the age & type ofcatalyst, the products desired, and the properties of the feedstocks.The primary operating variables are reactor temperature, reactorpressure, space velocity, and detrimental composition of the feed (i.e.contents of sulfur, oxygen, organic nitrogen, metals, & heavypolynuclear aromatics). The severity of the hydrocracking process ismeasured by the degree of conversion of the feed to lighter products.Typically, the net result of hydrocracking is 40 to 50 wt. % conversionof high boiling feedstocks to saturated cracked liquids withsubstantially lower boiling points (e.g. <400° F.). Hydrocracking alsoincreases volumetric yields up to 125%.

[0681] b. Prior Art; Hydrotreating of Gas Oils & Middle Distillates:

[0682] Hydrotreating refers to a class of hydroprocessing processes thatcatalytically stabilize petroleum products and/or remove objectionablecomponents in products or feedstocks via catalytic hydrogenation.Stabilization usually involves converting unsaturated hydrocarbons (e.g.olefins and unstable, gum-forming diolefins) to paraffins. Objectionablecomponents removed by hydrotreating include sulfur, nitrogen, oxygen,certain halides, trace metals, and aromatic compounds. Hydrotreatingprocesses employed for removal of a specific component includehydrodesulfurization (HDS), hydrodenitrification (HDN), andhydrodemetallization (HDM). Hydrotreating processes are applied to awide range of feedstocks, from naphtha to reduced crude. Unlikehydrocracking, the lower severity hydrotreating processes tend toinhibit cracking and to promote more selectivity.

[0683] Hydrotreating catalysts, particularly those for removal of aspecific component, tend to be more sophisticated than hydrocrackingcatalysts. Cobalt and molybdenum oxides on alumina catalysts aregenerally used due to their high selectivity, resistance to poisons, andease of regeneration. Cobalt-molybdenum catalysts are more selective tosulfur compounds. Nickel-molybdenum catalysts have higher hydrogenationactivity. Thus, they are preferable for nitrogen removal and saturationof aromatic rings. Other types of hydrotreating catalysts include nickeloxide, nickel thiomolybdate, tungsten sulfides, nickel sulfides, andvanadium oxide. In many applications, the catalysts must be activated byconverting the hydrogenation metals from the oxide to the sulfide form.Also, catalyst pore size is typically adjusted to improve and maintaincatalyst activity throughout the run cycle between regenerations.

[0684] Similar to hydrocracking, the hydrotreating processes typicallyare a fixed-bed, regenerative process, but often have a single reactorstage. The oil feed is usually mixed with hydrogen-rich gas before beingheated to the reactor inlet temperature: normally <800° F. to minimizecracking. As with hydrocracking, a hydrogen-rich gas is separated fromthe oil products and typically recycled with makeup hydrogen back to bemixed with feed at the heater inlet. Operating conditions in the reactorrange from 600 to 800° F. and 100 to 3000 psig. The space velocity(LHSV) ranges from 1.5 to 8.0. The temperature, pressure, space velocityand hydrogen consumption vary with the age & type of catalyst, thedesired feedstock improvements, and the properties of the feedstocks.Typically, hydrogen consumption is as follows: Sulfur Removal 70 scf/bblof feed for each wt. % sulfur Nitrogen Removal 320 scf/bbl of feed foreach wt. % nitrogen Oxygen Removal 180 scf/bbl of feed for each wt. %oxygen Aromatics/Olefins Reduction Stoichiometric amount based onrelative types

[0685] If operating conditions cause significant cracking, the hydrogenconsumption increases rapidly. Actual hydrogen makeup requirements are 2to 10 times the stoichiometric hydrogen required due to solubility lossin the oil products leaving the reactor and saturation of olefinsproduced by cracking. Hydrogen recycle is typically 2000 scf/bbl of feedto maintain sufficient hydrogen partial pressures. All reactions areexothermic. Depending on specific conditions, a temperature rise throughthe reactor of 5 to 20° F. usually occurs.

[0686] The primary operating variables of hydrotreating processes arereactor temperature, hydrogen partial pressure, and space velocity.Increasing temperature and hydrogen partial pressure increases desiredcomponent removal and hydrogen consumption. Increasing pressure alsoincreases hydrogen saturation and reduces coke formation. Increasingspace velocity reduces conversion, hydrogen consumption, and cokeformation. The severity of the hydrotreating process is measured by thedegree of conversion or removal of targeted feed components. Typically,the net result of many hydrotreating processes is the conversion ofundesirable feed components to <10 wt. %. Furthermore, volumetric yieldsdo not normally change to any significant degree, since the boilingpoints of the oil products are essentially the same as the feedstocks.That is, the boiling range of hydrotreated feedstocks does not changedramatically.

[0687] c. Prior Art; Hydroprocessing of Residuals:

[0688] In the last 20 years, numerous hydroprocessing technologies havebeen developed to prepare residual feedstocks for cracking and cokingunits. Atmospheric distillation tower bottoms, often called atmosphericreduced crudes or ARCs, are the primary feedstocks. The primary purposesof these hydroprocessing technologies are to reduce the boiling range ofthe feedstocks and/or remove substantial amounts of impurities,including metals, sulfur, nitrogen, and high carbon-forming compounds.Many of these hydroprocessing technologies are capable of 25 to 65% feedconversion rates. Common industry terminology for classes of thesehydroprocessing technologies also include hydroconversion,hydrorefining, and resid hydrodesulfurization (HDS). Trade names forspecific processes include Residfining, ARDS, VRDS, H-Oil, andLC-fining.

[0689] In general, these hydroprocessing technologies have similarprocess flow schemes and employ various types of catalytic reactors:fixed-bed, ebullated bed, or expanded bed. The latter two refer to acatalyst bed fluidized by a combination of gases and/or liquids.Typically, a guard reactor is followed by a series of hydroprocessingreactors. The guard reactor normally reduces the metals content and thecarbon-forming potential of the feed. The hydroprocessing reactors areoperated to remove sulfur and nitrogen and crack the 1050° F+materialsto lower boiling points. The reactors are designed for very low spacevelocities of 0.2 to 0.5 v/hr/v, limiting process flow rates. Operatingconditions in the reactors vary, but are typically maintained with inlettemperatures between 800 and 850° F. and pressures in the range of 2000to 3000 psig.

[0690] The catalysts in these hydroprocessing technologies can varysignificantly among technologies and applications of the sametechnology. The guard reactor catalyst is typically a silica-aluminacatalyst with large pore size (150-200 A°) and low loading ofhydrogenation metals (e.g. cobalt and molybdenum). The catalysts for theother reactors are tailor-made for the feedstock and conversion leveldesired. These catalysts generally have a wide range of particle sizes,various catalytic metal loadings and types. Pore sizes usually rangefrom 80to 100A°.

[0691] (2) Present Invention: Hydroprocessing of Petroleum Coke:

[0692] In the context of the current invention, hydroprocessing ofpetroleum coke refers to any process that uses hydrogen and/orcatalyst(s) at sufficient temperature and pressure to (1) reduce thequantity of coke via various types of hydrogenation and/or cracking ofcoke mass, (2) modify and/or improve coke crystalline structure &adsorption character, and/or (3) remove substantial amounts ofimpurities, including sulfur, nitrogen, metals, and high carbon-formingcompounds. This hydroprocessing of the petroleum coke can be processessimilar to hydrocracking, hydrotreating, and hydroprocessing ofresiduals in the prior art (described above).

[0693] Petroleum coke hydroprocessing can be done separately from thecoking process, but preferably within the coking process. That is,hydrogen can be injected into coke drums at the beginning of decokingcycles to initiate hydroprocessing of the pet coke in the coke drums. Inaddition, the petroleum coke does not necessarily have to be themodified pet coke of the current invention. Though the modified pet cokecan provide advantageous catalyst properties, other catalysts can beused instead or in addition. Preferably, this hydroprocessing can bedone in the presence of inexpensive catalysts, if needed. A carrierfluid (liquid and/or gas) can also be used to improve reactivity andoverall benefits. Primary purposes for coke hydroprocessing include:

[0694] 1. Reduce overall process coke yield via cracking & hydrogenationof coke compounds,

[0695] 2. Reduce sulfur, nitrogen, and/or metals (V, Ni, etc.) contentsof petroleum coke,

[0696] 3. Reduce coke yield & improve coke qualities via optimized cokeformation,

[0697] 4. Improve carbon adsorption character; approaching activatedcarbon, and/or

[0698] 5. Provide additional hydrotreating/hydrocracking capacity formiddle distillates.

[0699] High severity hydroprocessing of the prior art is not necessarilyrequired to achieve these objectives due to (1) lower conversionrequirements, (2) higher residence time, and (3) less liquid reactants.First, high conversion of the pet coke to cracked liquids is notnecessary for successful pet coke hydroprocessing. Incrementalimprovements are normally sufficient to achieve desirable benefits inmost refineries. That is, each ten-percent conversion in the cokehydroprocessing represents roughly 2.5 to 4.0% reductions in overallcoke yield, depending on coker feed quality. Thus, <10-15 wt. %conversion (vs. 25-65+wt. %) of coke mass to cracked liquids can besufficient to justify coke hydroprocessing, particularly within thedelayed coking process. However, greater conversions (e.g. 25-45%) canbe more desirable to further reduce overall coke yield and produce petcoke with superior carbon adsorption with much higher value. On theother hand, too much conversion can be detrimental to the modified petcoke crystalline structure and suboptimal. Secondly, high reactivity(e.g. fast reaction rates or strong reaction kinetics) and highselectivity are not required for the pet coke hydroprocessing either.This is particularly true if a third coke drum is added to increaseavailable coke cycle time and thus, hydroprocessing residence time.Thirdly, the system pressure requirements are typically less due tosignificantly less liquid character of the desired reactants. Themechanisms of hydrogen transfer with less liquid character cansignificantly reduce the required hydrogen partial pressure.Furthermore, the reduced liquid character of the reactants provideshigher hydrogen partial pressure at the same system pressures.Consequently, coke hydroprocessing can normally be successful with lowerquality catalysts and lower severity of operating conditions (e.g. muchlower hydrogen partial pressure) versus hydroprocessing of the prior art(e.g. hydrotreating, hydrocracking, & hydroprocessing of residuals).

[0700] a. Reaction Vessels:

[0701] The hydroprocessing of pet coke can be carried out in varioustypes of reaction vessels. New or existing coke drums in traditionalpairs of two can be sufficient reaction vessels for pet cokehydroprocessing. Alternatively, new reaction vessels separate form thedelayed coking process can also be used. Preferably, new coke drums inseries of three (vs. traditional pairs of 2) would provide additionaladvantages.

[0702] In some cases, existing or new coke drums in the current delayedcoking process can be sufficient reaction vessels for pet cokehydroprocessing. The semi-continuous, delayed coking process normallyhas pairs of coke drums with 2 cycles (coking & decoking). These issueswere briefly described in earlier sections. The coke mass in the cokedrum at the end of the coking cycle is already at or above the desiredtemperature (500 to 850° F; preferably 700 to 800° F.) for pet cokehydroprocessing. Hydrogen and catalyst can be added as needed, before,during, or after some initial coke cooling (if it is desirable). Inaddition, traditional coking cycles can be modified to providesufficient time for some pet coke hydroprocessing. However, this optionis often suboptimal due to current constraints in cycle times andequipment. Limited residence time for pet coke hydroprocessing canrequire faster reaction rates, limit pet coke hydroprocessingconversion, and reduce delayed coker throughputs. Faster reaction ratescan require higher hydrogen partial (and process) pressures. The currentcoke drums are often pressure limited (e.g. 100 psig) due to currentmetallurgy, delayed coker thermal cycles, and typical design parameters(e.g. head seals). New coke drums can alleviate the pressurelimitations, but have limited effect on time constraints.

[0703] In some cases, separate reaction vessels may be desirable toremove process pressure limitations and time constraints. These separatereaction vessels can be within or outside the current delayed cokerprocess boundaries. In most applications, pet coke hydroprocessingreaction vessels, that are not integrated into the delayed cokingprocess, are not usually practical due to excessive capital andoperating costs. The design challenge and fuel costs are oftenprohibitive for cooling the coke, removing it from the coke drums,transferring to other reaction vessels, and reheating the pet coke.Consequently, this option is not advantageous in most cases.

[0704] In many applications of this technology, the addition of a 3rdcoke drum with a third operating cycle may be the desired embodiment.The third coke drum in the series provides a third operating cycle inthe delayed coker: coke treatment (or hydroprocessing) cycle. That is,pet coke hydroprocessing (and/or other treatment options describedlater) is integrated into the delayed coking process. This third cokercycle can allow substantially more residence time for thehydroprocessing reactions, potentially reducing the required operatingseverity for a desired hydroprocessing conversion. In addition, part ofthe cooling in the traditional decoking cycle can be integrated into thepet coke hydroprocessing cycle, reduce overall coker cycle time, andincrease coker throughput capacity. For example, delayed coker cycles(coking, coke treatment, and decoking cycles) could be reduced to lowestpractical cycle times: 12-14 hours each. New coke drums (with or withoutnew materials technologies) and better mechanical seals can allow higheroperating pressures even with thermal cycles, structural stresses, andconsistent seal requirements. As discussed previously, new coke drumswould also provide the opportunity to implement advanced designfeatures, including (1) modified drill stem & top head seals for theaddition of chemical and/or thermal quenching agents during the cokingcycle to prevent vapors overcracking and (2) modified bottom head &skirting to remove coke in larger chunks for low-pressure dropapplications of adsorption carbon (e.g. utility boilers).

[0705] A basic process flow diagram for a delayed coker with three cokedrums is shown in FIG. 8. The delayed coking process equipment for thisembodiment of the present invention is similar to the prior art, withthe addition of a third parallel coke drum. However, the operation, asdiscussed below, is substantially different. This embodiment of thecurrent invention adds a third process cycle as well as a third parallelcoke drum. The modified delayed coking is still a semi-continuousprocess, but has three parallel coke drums that alternate betweencoking, coke treatment, and decoking cycles. The coke quench iscompleted in the treatment and/or decoking cycles. That is, the cokequench can be partially completed at the end of the coke treatment cycleand finished at the beginning of the decoking cycle to minimize and/oroptimize coker cycle times.

[0706] In the coking cycle, coker feedstock is heated and transferred tothe coke drum until full. Hot residua feed 810 is introduced into thebottom of a coker fractionator 812, where it combines with condensedrecycle. This mixture 814 is pumped through a coker heater 816, wherethe desired coking temperature (normally between 900° F. and 950° F.) isachieved, causing partial vaporization and mild cracking. Steam orboiler feedwater 818 is often injected into the heater tubes to preventthe coking of feed in the furnace. Typically, the heater outlettemperature is controlled by a temperature gauge 820 that sends a signalto a control valve 822 to regulate the amount of fuel 824 to the heater.A vapor-liquid mixture 826 exits the heater, and a 3-way control valve827 diverts it to a coking drum 828. Sufficient residence time isprovided in the coking drum to allow the thermal cracking and cokingreactions to proceed. By design, the coking reactions are “delayed”until the heater charge reaches the coke drums. In this manner, thevapor-liquid mixture is thermally cracked in the drum to produce lighterhydrocarbons, which vaporize and exit the coke drum. A control valvemechanism 829 is used to direct the outflows of the respective cokedrums and control system pressure (e.g. particularly during coke drumswitching). The drum vapor line temperature 830 (i.e. temperature of thevapors leaving the coke drum) is the measured parameter used torepresent the average drum temperature. Petroleum coke and someresiduals (e.g. cracked hydrocarbons) remain in the coke drum. When thecoking drum is sufficiently full of coke, the coking cycle ends. Theheater outlet charge is then switched from the first coke drum to aparallel coke drum to initiate its coking cycle. Meanwhile, thetreatment cycle begins in the first coke drum.

[0707] In the coke treatment cycle of the current invention, thepetroleum coke undergoes one or more of the various treatment options(e.g. hydroprocessing, coke extraction, chemical activation, etc.). Cokequench can be initiated during the treatment cycle. Quench media (e.g.steam) can be used at the beginning of the treatment cycle to cool thecoke drum to the optimal treatment temperature. Treatment agents (e.g.hydrogen & catalyst) can be injected into the drum at various injectionlocations 831, 832, and/or 834. After the coke treatment (e.g. cokehydroprocessing) is completed, additional quench can be achieved, ifcycle time permits. As described below, quench media can be injected atvarious locations: 831, 832, and/or 834. After the treatment cycle iscompleted, the coke drum passes (e.g. sometimes directly) into thedecoking cycle.

[0708] In the decoking cycle, the coke drum and its contents are furthercooled, the coke is drilled from the drum, and the coking drum isprepared for the next coking cycle. Cooling the coke normally occurs inthree distinct stages. In the first stage, the coke is cooled andstripped by steam or other stripping media 831 to economically maximizethe removal of recoverable hydrocarbons entrained or otherwise remainingin the coke. This first stage is optional, its degree of use dependingon the desired coke VCM content. In the second stage of cooling, wateror other cooling media 832 is injected to reduce the drum temperaturewhile avoiding thermal shock to the coke drum. Vaporized water from thiscooling media further promotes the removal of additional vaporizablehydrocarbons. In the final cooling stage, the drum is quenched by wateror other quenching media 834 to rapidly lower the drum temperatures toconditions favorable for safe coke removal. After the quenching iscomplete, the bottom and top heads of the drum are removed. Thepetroleum coke 836 is then cut, typically by hydraulic water jet, andremoved from the drum. After coke removal, the drumheads are replaced,the drum is preheated, and otherwise readied for the next coking cycle.

[0709] Lighter hydrocarbons 838 are vaporized, removed overhead from thecoking drums (primarily in the coking cycle), and transferred to a cokerfractionator 812, where they are separated and recovered. Coker heavygas oil (HGO) 840 and coker light gas oil (LGO) 842 are drawn off thefractionator at the desired boiling temperature ranges: HGO: roughly650-870° F; LGO: roughly 400-650° F. The fractionator overhead stream,coker wet gas 844, goes to a separator 846, where it is separated intodry gas 848, water 850, and unstable naphtha 852. A reflux fraction 854is often returned to the fractionator.

[0710] b. Theory of Operation:

[0711] In general, hydroprocessing of petroleum coke combineshydrogenation and cracking reactions with or without catalyticactivation. Overall, this hydroprocessing has complex reaction chemistrydue to the complex nature of the chemical compounds and catalystsinvolved. That is, numerous complementary and competing chemicalreactions take place in pet coke hydroprocessing. The primary reactionmechanisms in typical applications are described as part of a simplifiedtheory of operation. However, this theory of operation may notaccurately describe all applications, and should not limit the currentinvention. Hydrogenation and various cracking mechanisms (e.g. thermal,catalytic, & hydrogenolysis) are generally discussed, along with theirinteraction in this process. The impacts of key operational parameters(e.g. system temperature, catalyst activity, hydrogen partial pressure,and residence time) are also discussed.

[0712] At the end of the coking cycle in the delayed coking process, thepetroleum coke is normally a semi-solid (or semi-liquid) coke mass. Thatis, much of the coke mass at temperatures of 800 to 900° F. andpressures >25 psig has solidified crystalline growth from thermalcracking in the absence of hydrogen. This pet coke crystalline growth iscaused by various reactions: including dehydrogenation, condensation,oligomerization, aromatization, polymerization, and/or cross-linking ofheavy compounds in the coking cycle. However, some materials remain aheavy, pitch-like liquid, until cooled further. These pitch-likematerials are expected to be primarily asphaltenes with some resins andother heavy aromatics. These materials are usually solutized, but notyet chemically/physically attached to the coke crystalline structure.Higher coke crystalline contents (e.g. lower asphaltenes/resins toaromatics ratio) are more favorable for coke hydroprocessing due togreater adsorption and catalytic properties within its substantiallevels of porous, solid coke at these conditions. At lower temperatures,a greater portion of coke mass can become solid crystals with morefavorable adsorption and catalytic properties.

[0713] As noted previously, less graphitizable carbon structures areoften more susceptible to hydrogenation reactions (i.e. reversibledehydrogenation reactions) than anode-grade, sponge coke. The degree ofthe non-graphitizable carbon character apparently depends on the degreeof mesophase transition in the coking process. In turn, this degree ofmesophase transition greatly depends on the chemical composition of thecoker feedstocks and the coker operating conditions, particularlytemperature profiles. The modified pet coke of the current invention(discussed previously) is the desired embodiment for thishydroprocessing treatment due to its less graphitizable character.However, a carbonaceous material with even less graphitizable charactercan be preferable under certain conditions. For example, a porous,carbonaceous material (e.g. semicoke) intermediate between mesophasepitch and a non-deformable green coke can be more susceptible to thehydrogenation reactions of this coke hydroprocessing. Conceivably, thisembodiment would optimize coker feeds and operating conditions to obtainthe carbonaceous material with the lowest carbon to hydrogen ratio(C/H), while maintaining a porous, crystalline structure (vs. pitch-likematerials).

[0714] b1. Hydrogenation:

[0715] The addition of hydrogen to this semi-solid, coke mass willnormally initiate some degree of hydrogenation of olefinic, aromatic,and/or heterocyclic compounds in the coke mass. Hydrogenation isgenerally a class of reactions that breaks double bonds and saturatesthe reactant (e.g. multi-ring aromatics) with hydrogen. Thehydrogenation reaction mechanism usually follows free-radical chainreactions, where free-radicals are highly reactive intermediates whichhave an unpaired electron. In hydrogenation, the free-radical istypically atomic hydrogen (vs. molecular hydrogen H₂). The porous petcoke in the semi-solid coke mass has a strong tendency to breakmolecular hydrogen into atomic hydrogen with an unpaired electron. Thatis, adsorption of hydrogen on the pet coke's internal surfacecatalytically promotes the breakdown of molecular hydrogen (bond energy:103 kcal/mole) into hydrogen free-radicals. A similar reaction mechanismwas discussed previously for the breakdown of molecular oxygen (bondenergy: 117 kcal/mole) in the use of activated carbons or modified petcokes as an oxidation catalyst. In this manner, hydrogen free-radicalsare readily available and migrate on the surface of the pet coke, whichis also the desired reactant in the hydrogenation. The degree of petcoke hydrogenation depends on various factors, including (1) coke masscomposition, (2) catalyst activity, (3) temperature, (4) hydrogenpartial pressure, and (5) residence time.

[0716] Residence time discussion: 0.5 to 12 hours vs. residence timesusually <1.0 hour. Thus, reaction rate is not as critical as long assufficient equilibrium driving force is present for reactions to occur.Excess hydrogen will tend to drive equilibrium in favor ofhydrogenation.

[0717] The composition and reactivity of the semi-solid, coke mass canhave substantial impact on the degree of pet coke hydrogenation. Asnoted above, the pet coke mass typically consists of polyaromatics,resins, and asphaltenes. As such, the primary focus of this discussionwill be the hydrogenation of aromatic compounds. The resonancestabilization energy of most aromatic bonds renders them unbreakable atprocess temperatures <1100° F. until the aromatic character is destroyedby hydrogenation. Limited hydrogenation occurs in the delayed cokingprocess due to lack of hydrogen and hydrogenation catalysts. As aresult, these aromatic compounds are concentrated in the coke mass fromdehydrogenation and coking reactions. In contrast, the hydroprocessingof pet coke promotes the hydrogenation and subsequent cracking of thesepolyaromatic compounds. The hydrogenation reaction is morethermodynamically favorable for compounds with greater number of ringsand irregularity (e.g. less symmetry) in the aromatic clusters. That is,hydrogenation is favored in polyaromatics with lower average resonanceenergy per bond or weaker bonds. Thus, the asphaltenes and resins in thepitch-like materials are normally more likely to undergo hydrogenationthan the polyaromatics in the crystallized coke due to weaker bonds, asevidenced by its more liquid character (e.g. lower melting point). Ifpredominant hydrogenation of the asphaltenes and resins occurs withsubsequent cracking, the lower asphaltenes/resins to aromatics ratiowill create a more highly porous, sponge coke. Consequently, the cokemass catalyst activity will increase as the asphaltenes and resins arehydrogenated and cracked. Ultimately, the hydroprocessing of the petcoke will provide even better coke crystalline structure with greateradsorption character.

[0718] Since hydrogenation and dehydrogenation are reversible reactions,the excess concentrations of hydrogen and aromatic compounds in pet cokehydroprocessing tend to drive the reaction strongly in favor ofhydrogenation.

[0719] Hydrogenation reactions are not too sensitive to temperaturewithin the considered temperature ranges of pet coke hydroprocessing:500-1000° F (preferably 700-800° F.). Hydrogenation is an exothermicreaction, and equilibrium yields are favored by relatively lowtemperatures. However, reaction rates increase with temperature.Hydrogenation of polyaromatic compounds becomes a compromise betweenusing low temperatures to achieve maximum reduction of aromatic contentand high temperatures to provide high reaction rates and minimizecatalyst charge per barrel of feed. Maximum aromatic reduction isnormally achieved between 700° F. and 750° F. due to the interrelationof thermodynamic equilibrium and reaction rates. However, higherreaction rates and associated high temperatures are less important withample residence time. Thus, lower temperatures can also providedesirable conversion levels with longer residence times. Furthermore,lower temperatures would solidify more of the coke mass, which canprovide more favorable adsorption and catalytic characteristics. Thus,coke hydroprocessing objectives and the coke mass composition & physicalcondition play a significant role in determining the optimaltemperature. In general, the optimum temperature, for a given pressure,is a function of the types of aromatic compounds in the coke mass,residence time, hydrogen concentration, and catalyst considerations(e.g. amount & cost).

[0720] Increasing the hydrogen partial pressure generally increases thedegree of hydrogenation reactions. As discussed in the prior art, thereaction kinetics of hydrogenation reactions is more favorable withhigher hydrogen partial pressure. In fact, hydrogen partial pressure isthe most important parameter controlling traditional aromaticsaturation. Traditional hydroprocessing (e.g. hydrocracking &hydrotreating) relies heavily on very high hydrogen partial pressures tocreate fast and effective transfer of hydrogen from the gas phase to theliquid phase of the reactants. That is, the high hydrogen partialpressure promotes hydrogen free-radicals in the liquid phase via variousmechanisms, including hydrogen solubility, aromatic solvents and cyclesof hydrogenation & dehydrogenation. In contrast, the hydroprocessing ofpet coke behaves more like solid-gas phase reactions, more similar toadsorption processes. Molecular hydrogen is typically adsorbed by theporous coke in the coke mass and catalytically converted to hydrogenfree-radicals. The carbon adsorption character (e.g. Van der Waalforces) of the pet coke mass allow the relatively unrestrained migrationof hydrogen free-radicals. That is, hydrogen access to the polyaromaticcompounds in the coke mass is less inhibited by excess liquid flow offeed in the prior art. In other words, the primary reactants (coke mass)in the hydroprocessing of pet coke are in a semi-solid state that doesnot fill the voids of the reaction vessel with a free flowing liquid.Hence, the hydrogen free-radical transfer mechanism of the pet cokehydroprocessing is substantially less dependent on the hydrogen partialpressure. Also, the hydrogen has a significantly higher molarconcentration, since it is the primary fluid that causes the increasedsystem pressure. Thus, the partial pressure of hydrogen required can beachieved at lower system pressures versus the prior art forhydroconversion processes. Furthermore, longer residence times in thecurrent invention (discussed later) further reduce the need for fasthydrogen transfer mechanisms (vs. prior art), and require even lesshydrogen partial pressure. Finally, the lower conversion requirementsfor acceptable operation also reduces the need for the high hydrogenpartial pressures of the prior art. In many cases, the highest practicalsystem pressure may be desired to increase hydrogen partial pressure,but not necessarily required to aftain sufficient hydrogen transfer inpet coke hydroprocessing.

[0721] In many cases, the hydrogenation catalyst activity of the porous,sponge coke in the coke mass is sufficient to initiate hydrogenation ofthe asphaltenes, resins, and other polyaromatics in the coke mass.However, in some cases, other catalysts or additives with additionalhydrogenation catalytic activity may be necessary to cause sufficienthydrogenation initially. The primary role of other catalysts oradditives would be to enhance the formation and transfer of hydrogenfree-radicals and inhibit dehydrogenation & coking reactions. Goodhydrogenation catalysts tend to be acidic, and are susceptible topoisoning, particularly with nitrogen. A variety of transition metals(e.g. iron, nickel, cobalt, molybdenum, tin, & tungsten) providefavorable hydrogenation catalyst characteristics in this processenvironment. That is, these metals are reactive in the sulfide form, aswell as the metallic state. Traditional hydrogenation catalysts (e.g.Co/Mo and Ni/Mo) can be technically feasible for pet cokehydroprocessing (e.g. can be impregnated on the coke), but would likelybe too costly as a non-recoverable coke additive. More likely, ironcompounds would be used as powdered or impregnated additives, due totheir very low costs. For example, iron oxide will likely be convertedin-situ to the sulfide form, and promote hydrogen transfer reactions.Iron sulfate is also an effective additive. In some cases, minoradditions of iron sulfate may be desirable to initiate hydrogenationreactions, until sufficient sulfur is generated from the coke mass toreact with predominate iron oxide additives. The injection of thesecatalyst/additives can be achieved by various means. For example, finelypowdered additives can be added to the coke during the coking cycle orinjected in to the coke with hydrogen or steam at the beginning of thepet coke hydroprocessing. In many cases, finely powdered additives canbe preferably added via a cooling media, such as used lubricating oilsor heavy gas oils, that vaporize (e.g. >700° F.) and distributes theadditives in the coke mass in a fairly uniform manner.

[0722] Hydrogen circulation rates are typically 3-4 times thestoichiometric amount of hydrogen consumption. Hydrogen sulfideconcentrations tend to inhibit hydrogenation of aromatic rings andammonia tends to decrease hydrocracking conversion. Therefore, continualremoval of ammonia and hydrogen sulfide via continual mass transfer awayfrom coke mass reaction sites is preferable. For example,

[0723] b2. Cracking Reactions:

[0724] Various cracking reactions are complementary to the hydrogenationreactions. That is, the exothermic hydrogenation reactions (1) usuallyprovide more than enough heat for the endothermic cracking reactions,and/or (2) produce intermediate compounds that are more readily cracked.In the latter, the resonance stabilization of many aromatic bondsrenders them unbreakable at normal process temperatures (<1100° F.)until the aromatic character is destroyed by hydrogenation. That is, thehydrogenation reactions can lower the bond dissociation energies foreasier cracking. On the other hand, the cracking reactions can (1)provide olefinic & aromatic intermediates for hydrogenation and/or (2)create access to heterocyclic compounds, deeply imbedded in theasphaltenes and resins of the coke mass. These heterocyclic compoundsoften contain undesirable impurities (e.g. S, N, & metals). The majortypes of cracking reactions in pet coke hydroprocessing include thermalcracking, catalytic cracking, and hydrogenolysis. As with hydrogenation,the cracking reactions are more likely for complex compounds with morearomatic rings, less symmetry, and some aliphatic character (e.g.bridges). Consequently, asphaltenes (solutized or otherwise) in the cokemass have a greater tendency (vs. aromatics and resins) to bothhydrogenate and crack due to their higher molecular weights andcomposition.

[0725] As the exothermic hydrogenation reactions proceed, sufficientheat is generated to initiate additional thermal cracking. The net heatgenerated typically creates excess heat that raises the reactortemperature and accelerates the cracking reaction rates, until quenchedor controlled (via cold hydrogen or other quench mechanisms). Asexplained in the prior art of delayed coking, the hierarchy of ease ofthermal cracking is Paraffins>Linear Olefins>Napthenes>CyclicOlefins>Aromatics. Again, resonance stabilization of many aromatic bondsrenders them unbreakable at normal process temperatures (<1100° F.).Thus, the aromatic compounds still are not likely to be thermallycracked in the pet coke hydroprocessing (similar to delayed coking).However, thermal cracking can crack the cyclic olefins and napthenes,produced by hydrogenation of aromatic compounds, if temperatures aresufficient. Temperatures of 800-900+° F. would be required to thermallycrack many of these compounds. As with delayed coking, processtemperatures >800° F. can lead to dehydrogenation, coking, and vaporovercracking (i.e. light gases versus cracked liquids). Fortunately, theexcess of hydrogen inhibits these undesirable reactions, even at higherthermal cracking temperatures. In addition, most of the coke-formingcompounds have already become coke in the more severe delayed cokingprocess. That is, additional coke formation in the pet cokehydroprocessing is not likely.

[0726] The addition of certain catalyst materials.can lower theactivation energies of the cracking reactions, reducing processtemperature requirements and/or increasing cracking reactivity of moretroublesome compounds. Heterogeneous catalysts bearing acid sites canaccelerate the rate of cracking at a given temperature and/or improvethe selectivity toward stable products. As with prior art hydrocracking,pet coke hydroprocessing combines hydrogenation and catalytic crackingvia a bi-functional catalyst. However, unlike hydrocracking, thesemi-solid, coke mass (i.e. porous coke crystals & pitch-like materials)acts as a cracking catalyst and has substantially less resistance tohydrogen diffusion and alignment of reactants (pitch-like materials) tothe catalyst sites (porous coke crystals). Also, the hydrogen radicalformation & transfer (e.g. migration) and reaction mechanism behavesmore like gas-solid phase reactions in adsorption carbon. Consequently,catalytic cracking reactions can be normally achieved at lower hydrogenpartial pressure (& system pressure) and/or lower temperatures. This isparticularly true for applications where conversion requirements arelower and residence times are significantly higher. If greater catalystactivity is needed, additives can be impregnated on the base catalyst(i.e. porous coke crystals) via various mechanisms. In many cases,sufficient catalytic cracking can be achieved at temperatures of 500° F.to 950° F. (preferably 700° F. to 750° F.) and pressures of 15 to 2000psig (preferably 15 to 100 psig). If more catalyst activity is neededfor a given catalyst, increased temperatures and/or pressures can beeffective. In any case, the catalyst formulation and operatingconditions are normally optimized for each application, depending oncoke mass composition and desired objectives. This approach is similarto hydrocracking of the prior art.

[0727] Another type of cracking reaction in pet coke hydroprocessing ishydrogenolysis; cleavage of bonds by hydrogen addition. Inhydrogenolysis, radical hydrogen transfer reactions can provide analternative mechanism for cracking strong bonds (e.g. C═C; thiophenicC—S), including degradation of aromatic groups. In the prior art, thetransfer of free-radical hydrogen by an aromatic solvent can achievethis type of cracking. In addition, the migration of hydrogen radicalsfrom the catalyst surfaces has also been noted to promotehydrogenolysis. Similar hydrogenolysis reaction pathways exist in thepet coke hydroprocessing. Hydrogenolysis reactions can be enhanced inpet coke hydroprocessing due to (1) less resistance to hydrogen radicaltransfer, (2) longer residence times, and/or (3) higher concentration ofaromatic groups in the coke mass. Further enhancement of hydrogenolysiscan be achieved at higher catalyst activity and/or higher hydrogenpartial pressure.

[0728] b3. Conversion of Heteroatomic & Organometallic Compounds:

[0729] As the asphaltenes and resins hydrogenate and crack, heteroatomicand organometallic compounds are normally exposed for further treatment.Hydrogenation of these compounds is more readily achieved than in theprior art. That is, the hydrogenation and subsequent cracking ofaromatics in the pet coke hydroprocessing provide access and favorablereaction conditions to hydrogenate heteroatomic and organometalliccompounds that have been traditionally inaccessible (deep within theorganic structures of asphaltenes and resins). In this manner, sulfur,oxygen, and nitrogen in the heteroatomic compounds can be transformed tohydrogen sulfide, water, and ammonia, respectively. These gaseouscompounds can then be removed from the pet coke mass and treatedfurther. The metals in the organometallic compounds can be hydrogenatedto yield metal sulfides that normally remain with the coke mass. Thedegrees of conversion for each type of compound will depend on variousfactors, including (1) pet coke mass composition, (2) degree of aromatichydrogenation and subsequent cracking, (3) local hydrogenation catalystactivity and type, and (4) hydrogen availability at reaction sites(hydrogen partial pressure or otherwise). Conversion of manyheteroatomic and organometallic compounds often enhances the ability tofurther hydrogenate and/or crack the products of these conversionreactions.

[0730] Exposed sulfur compounds are readily converted to hydrogensulfide via hydrogenation and hydrogenolysis. Most of the non-thiophenicsulfur compounds, such as sulfides, thioethers, thiols, and mercaptans,are normally converted to hydrogen sulfide by thermal reactions in thecoking cycle of the delayed coking process. The thiophenic sulfur isnormally unaffected by thermal reactions, and typically requirescatalytic hydrodesulfurization. In the pet coke hydroprocessing,thiophenic sulfur compounds and remaining non-thiophenic sulfurcompounds are converted to primarily hydrogen sulfide and othernon-thiophenic sulfur compounds. Both hydrogenation and hydrogenolysismechanisms can effectively convert the thiophenic sulfur.

[0731] Similarly, exposed oxygen compounds are readily converted towater via hydrogenation. Aromatic hydroxyl and furan compounds are thepredominant oxygen compounds remaining after the thermal reactions inthe coking cycle of the delayed coking process. In the pet cokehydroprocessing, hydrogenation can readily convert these compounds towater, which can be subsequently removed from the process.

[0732] Exposed nitrogen compounds are much less reactive, but can beconverted to ammonia via hydrogenation with the proper catalyst activityand operating conditions. The nitrogen compounds remaining in the cokemass are primarily two types: (1) non-basic derivatives of pyrrole (e.g.pyrroles, indoles, & carbazoles) and (2) basic derivatives of pyridine(e.g. pyridines, quinolines, & acridines). Catalysts containing nickel(Ni/Mo or Ni/Co/Mo) tend to promote hydrodenitrification, buthydrodesulfurization will occur also. However, unlike catalyticdesulfurization, only the hydrogenation reaction mechanism is prominentin catalytic hydrodenitrification. The hydrogenation catalyst sites aremore acidic than the hydrogenolysis catalyst sites, and hence tend to bepoisoned by adsorption of the basic nitrogen compounds. Apparently, thesynergistic effects of hydrogen sulfide from hydrodesulfurization andwater from hydrodeoxification can further promote hydrodenitrificationby increasing the catalyst acidity.

[0733] Hydrogenation of exposed organometallic compounds typically formsdeposits of metal compounds on the catalyst(s). Metals occur in twobasic organic forms: porphyrin metals and non-porphyrin metals.Porphyrin metals, which are chelated in porphyrin structures analogousto chlorophyll, have porphyrin rings, based on pyrrole groups whichcomplex the metal atom. The non-porphyrin metals (e.g. metalnaphthenates) are thought to be associated with the polar groups inasphaltenes. Metal removal typically occurs during both thermal andcatalytic processing. However, removal is more complete when a catalystprovides much more effective hydrogen transfer. In pet cokehydroprocessing, the organometallic compounds, such as porphyrins andmetal naphthenates, can decompose and transform to metal sulfides (e.g.nickel, iron, and vanadium sulfides) in a colloidal state with particlesizes ranging form 20 to 250 nm. These metal sulfides can enhancehydrogenation catalyst activity and increase hydrogen availability andreactivity. However, these metal sulfides (e.g. rod-like crystals ofvanadium sulfide: V₃S₄) can accumulate and cover the catalyst surfaceand/or block macropores in the catalyst/support structure. Fortunately,the pet coke mass in the pet coke hydroprocessing normally hassufficient macropore structure in the porous, pet coke to accommodatehigh conversions of metals to metal sulfides. That is, the weight ratioof porous, pet coke to metals content of the coke mass istypically >100:1. As such, the accumulation of metal sulfides on the petcoke mass does not normally inhibit its catalytic activity, but enhancesit.

[0734] c. Residence Time:

[0735] The residence time of pet coke hydroprocessing reactions can varyconsiderably, depending upon the selection of reaction vessel(s) foreach application. As discussed previously, the reaction vesselconsiderations provide three potential scenarios for the pet cokehydroprocessing: (1) coke drums (existing or new) in the traditionaldelayed coking configuration (i.e. 2 coke drums & 2 coking cycles), (2)existing/new coke drums in a modified configuration (i.e. 3 coke drums &3 coking cycles), or (3) new reaction vessel(s) in a separate pet cokehydroprocessing unit.

[0736] If coke drums are used in the traditional delayed cokingconfiguration. the residence time of pet coke hydroprocessing reactionscan be limited: <15 minutes to >2 hours. The optimal residence time willdepend on design and operating constraints of the existing delayedcoking cycles, as well as the required time to achieve site-specific,pet coke hydroprocessing objectives. Equipment constraints, such as cokedrum pressure limitations and coker subsystem bottlenecks can alsoinfluence sufficient residence time.

[0737] Residence time limits in the pet coke hydroprocessing can bedramatically loosened by the use of 3 coke drums (existing and/or new)in 3 coking cycles. In this reaction vessel scenario, the residence timecan be as long as the existing coking cycle (e.g. 12-16 hours). However,lower residence time for pet coke hydroprocessing is more likely toallow (1) movement of traditional decoking cycle tasks to the pet cokehydroprocessing cycle and/or (2) additional distillate/gas oilhydrotreating capacity in the pet coke hydroprocessing cycle. In thiscase, the time for each cycle time can be reduced and increase coke feedthroughput capacity.

[0738] The pet coke hydroprocessing residence time has few designlimits, if new reaction vessel(s) is/are built for a separate pet cokehydroprocessing unit. However, the residence time impact on costs can beprohibitive in achieving an acceptable return on investment(s).

[0739] d. Catalysts:

[0740] Unlike the hydroprocessing of the prior art, the petroleum cokeis not only the process feed, but can also play a major role in thecatalysis of the desired reactions. That is, the pet coke (1) behaves asa hydrogenation catalyst, (2) acts as a cracking catalyst, (3) providessurface area for catalyst impregnation, and/or (4) produces metalsulfide hydrogenation catalysts. The porous pet coke in the coke masscan also provide a bi-modal distribution of catalyst pores to enhanceits catalytic cracking activity. In addition, the pet cokehydroprocessing conditions limit catalyst deactivation. In this manner,the porous pet coke in the coke mass provides bifunctional catalystproperties and deactivation resistance required for pet cokehydroprocessing.

[0741] The pet coke can perform the function of a hydrogenationcatalyst. As discussed previously, sponge, pet coke with sufficientcarbon adsorption character can adsorb oxygen molecules and break themdown into reactive ion radicals. Similarly, this sponge coke can alsoadsorb hydrogen molecules and break them down into reactive ionradicals. This is particularly true for the highly porous spongestructure of the modified pet coke in the current invention. That is,the lower asphaltene/resin to aromatics ratio normally provides lessliquid and more solidified, porous sponge coke in the coke mass.

[0742] The solidified, porous crystalline structure of the semi-solidcoke mass can act as a cracking catalyst, too. In many ways, the largeinternal surface area of highly porous, sponge coke behaves likesilica-alumina in its adsorption capabilities. The adsorption andbreakdown of hydrogen molecules provides the rapid transfer of reactivehydrogen radicals to (1) catalyze thermal cracking reactions at loweractivation energies and temperatures and (2) directly break strong bondsvia hydrogenolysis. As pet coke hydroprocessing proceeds, the spongecoke portion of the coke mass increases, as well as its porosity,adsorption character, and catalytic activity. Thus, the catalyticcracking activity can normally accelerate.

[0743] The solidified, sponge coke portion of the coke mass providesporous surface area for: the impregnation of various catalyst enhancingcompounds. If the pet coke does not provide sufficient catalyticactivity to initiate sufficient hydrogenation and/or cracking, theporous sponge coke can be impregnated (or seeded) with finely divided,catalytic additives (e.g. Ni, Co, Mo, Fe). However, the recovery ofthese catalytic additives would be difficult and expensive. Therefore,less expensive catalytic additives, such as iron sulfate or iron oxidewastes, would be preferable. Furthermore, fine particles ofsilica-alumina can also be added to the coke mass to increase catalyticcracking activity, if needed. In addition, other additives can be usedto enhance catalyst activity, such as increased acidity of the reactionsites. For example, acidity can be increased by substitution reactionsincreasing the concentration of alkaline earth metals, rare earthmetals, or hydrogen.

[0744] The hydrogenation of heteroatomic and organometallic compoundscan produce additional hydrogenation catalysts. As discussed previously,metal sulfides (i.e. sulfides of Ni, Fe, & V) can form from the chemicalcombination of sulfur and metals from hydrogenation of organic sulfurand metal compounds in the coke mass. These metal sulfides can be goodhydrogenation catalysts to a limited extent. In excess, these metalsulfides can block catalyst pores and poison certain catalysts. However,the metal sulfides are limited by the concentration of the metals in thecoke mass in this (semi-continuous or batch) process. Since the metalscontent of the coke mass is typically <0.2% by weight, the accumulationof metal sulfides is not normally sufficient to cause significantdetrimental impacts. Thus, the net effect typically favors increasedhydrogenation activity.

[0745] The pet coke hydroprocessing operating conditions limit catalystdeactivation by coke fouling and/or poisoning by nitrogen, oxygen, ormetals. Catalysts in pet coke hydroprocessing are not as susceptible tocoke fouling. Compounds having coke forming tendencies have alreadybecome coke in the coke mass. Therefore. not likely to foul catalystwith additional coke formation in the presence of hydrogen.

[0746] Bi-functional catalyst can be formulated to meet thesite-specific objectives and constraints for each application of petcoke hydroprocessing.

[0747] e. Overall Process: Interaction of Various Reactions:

[0748] In the pet coke hydroprocessing, a formidable combination ofvarious reactions and chemical species usually occur simultaneously.These reactions potentially include (1) various types of hydrogenationreactions with aromatic compounds, olefins, and heterocyclic compounds(i.e. containing sulfur, oxygen, nitrogen, and/or various metals), (2)various types of cracking reactions: thermal, catalytic, andhydrogenolysis, and (3) various types of coke-forming reactions:dehydrogenation, condensation, aromatization, oligomerization,polymerization, and cross-linking. The complexity of reaction mechanismsis further complicated due to simultaneous thermal and catalyticreactions (cracking & otherwise). Consequently, selecting catalysts andoperating conditions that enhance desirable reactions and/or inhibitundesirable reactions is critical to achieve objectives in eachapplication of pet coke hydroprocessing. As discussed previously, othersite-specific factors and constraints can have significant impacts onthe optimization of pet coke hydroprocessing. These site-specificfactors (and associated examples) include, but should not be limited to:

[0749] 1. Coke Mass Composition and Physical Properties: SARA;hetero-contents; % solid, porosity

[0750] 2. Reaction Vessel Constraints: Number; new/old; pressurelimitations;

[0751] residence time

[0752] 3. Coke Product Specifications: Fuel requirements; adsorptioncarbon characteristics; other

[0753] 4. Economic Constraints: Capital and operating costs, productvalues; acceptable conversion

[0754] The basic interaction of process temperature, hydrogenavailability, and catalyst activity are shown in the simplified diagramof FIG. 9. The points of the triangle represent the highest value foreach variable, and the opposite side represents minor to negligiblevalue for that same variable. In the delayed coking process, the processtemperature (e.g. 850-925° F.) is near its highest practical value (i.e.lower left point of triangle), while catalyst activity and availablehydrogen (e.g. partial pressure) are minor to negligible. Thus, theprimary reactions of residual components are dehydrogenation and coking;forming the coke mass of concern in the pet coke hydroprocessing. Asseen in this diagram, hydrogenation can be preferentially achieved byincreasing the hydrogen availability (e.g. hydrogen partial pressure orotherwise) and catalyst activity, while decreasing temperature. Ifpressure limitations of the reaction vessel limit the hydrogenavailability, then higher catalyst activity with lower processtemperatures can maintain operation in the hydrogenation regime: Zone 1Operating Conditions. If the coke drums are modified to remove pressurelimits (e.g. new drums w/advanced metallurgy and proper thickness), thehydrogenation operating regime can be maintained with higher hydrogenavailability and lower temperatures, in lieu of higher catalystactivity. These operating conditions are represented by Zone 3 in FIG.9. The coke drums in many existing coker applications can have limitedhydrogen availability (e.g. drum pressure limits) and catalytic activity(e.g. less ability to impregnate coke w/catalyst). In these cases, Zone2 operating conditions may be preferred due to higher reliance ontemperature versus hydrogen availability or catalyst activity. As notedpreviously, different feeds can result in different operating regimes(e.g. hydrogenation vs. dehydrogenation), even at identical operatingconditions (i.e. temperature, hydrogen availability, & catalystactivity). Thus, this diagram has limited use for absolute values of therespective operating conditions, but provide their relative impacts onthe hydrogenation operating regime. Consequently, pilot scale tests areoften needed to refine operating conditions of this technology for agiven feed. The preferable operating conditions would be in thehydrogenation operating regime, at a point where the overall processprofitability is maximized, based on site-specific operatingconstraints.

[0755] The interactions between catalytic and thermal reactions with thevarious residual compounds can be very complex. Some of the reactionsare reversible. Their reaction mechanisms and equilibrium can often bedetermined by the (1) specific compounds & impurities in feed, (2)quality & quantity of catalyst(s), and (3) various process conditions,including process temperature & hydrogen partial pressure. For example,polyaromatics, in the presence of hydrogen and catalyst(s), can undergocycles of hydrogenation and dehydrogenation. Furthermore, crackingreactions would proceed via various free-radical reaction mechanisms,including abstraction of aliphatic, napthenic, and aromatic hydrogenatoms, along with hydrogenolysis. Catalyst activity for bothhydrogenation and hydrogenolysis may depend greatly on the transfer ofhydrogen radicals. Thus, interaction of hydrogenation and hydrogenolysismay be a key parameter that may be addressed on a case-by-case basis. Asuggested way to look at optimization of the current technology tospecific applications is FIG. 9.

[0756] Optimal pet coke hydroprocessing of the current invention wouldoften inhibit coke-forming reactions and promote certain hydrogenationand cracking reactions. The hierarchy of desirable reactions for manyapplications of pet coke hydroprocessing likely includes:

[0757] 1. Hydrogenation & cracking of asphaltenes & resins: Reduce cokeyields; Better coke quality

[0758] 2. Iterative hydrogenation/catalytic cracking of intermediates:Improve liquids yield; Inhibit gas

[0759] 3. Hydrogenation/hydrogenolysis of sulfur compounds:Substantially improve coke quality

[0760] 4. Hydrogenation of nitrogen compounds: Improve coke fuelquality; reduce catalyst poison

[0761] 5. Hydrogenation of organometallic compounds: Enhance catalystactivity; limited coke effect

[0762] 6. Hydrogenation of oxygen compounds: Reduces coke fuel quality;impacts adsorption quality

[0763] In many of these cases, the desirability of the last three typesof reactions is questionable. Fortunately, these three types ofreactions are more difficult to achieve on a thermodynamic basis. Thus,the remaining discussion will focus on the first three types ofreactions.

[0764] These complementary hydrogenation and cracking reactions proceeduntil the desired conversion of the coke mass is achieved: production ofcracked components with lower boiling points and/or the removal ofundesirable impurities, including sulfur and nitrogen. The gasesgenerated (hydrocarbons w/ B.P. <850° F., hydrogen sulfide, ammonia, andwater) are released or withdrawn form the reaction vessel with excesshydrogen. Similar to hydroprocessing of the prior art, the gases areseparated by high and low pressure flash separators: the hydrocarbonsare sent to a fractionator system, while the overhead gases are passedthrough an amine stripper. The hydrogen rich gas is recycled and therich amine solution goes to the sulfur plant for further processing.When the reactions are sufficiently complete, the reactor can bedepressurized and quenched. After cooling to roughly 200° F., the cokecan be safely removed from the reactor vessel.

[0765] Simultaneous hydrogenation and cracking of the coke mass areinitiated and proceed with sufficient residence time to obtain thedesired conversion. As the hydrogen enters the system, the very porous,solidified coke within the coke mass (and its increased adsorptioncharacter in this exemplary embodiment) convert the molecular hydrogento free radical ions without catalyst additives. As discussedpreviously, the adsorption character of the coke mass and the solid-gasphase nature of coke hydroprocessing make the hydrogen free radicalsreadily available for migration to the reaction sites without excessivehydrogen partial pressure. The reaction sites are normally the surfaceof the reactants (e.g. asphaltenes, resins, & condensed aromatics). Thehigh concentrations of both reactive molecules and hydrogen freeradicals create driving forces for high degrees of complementaryhydrogenation and cracking reactions. Normally, the hydrogenation andcracking reactions preferentially attack the weaker bonds of theasphaltenes and resins. Significant breakdown and removal of complexaromatic compounds (preferably asphaltenes and resins) from the cokemass create additional voids in the coke crystalline structure. The sizeof these voids range form <2 nanometers to >50 nanometers. As a result,additional micropores, mesopores and macropores. This is analogous tothe removal of basal planes in the steam activation of carbonizedcarbons to produce high-quality activated carbons. Ample residence timeof the exemplary embodiment allows lower operational temperatures thatfavor greater aromatic saturation.

[0766] In most cases, the resulting petroleum coke has significantlyless mass, lower density, higher porosity, and greater carbon adsorptioncharacter. The cracking and hydrogenation of heavy compounds (preferablyasphaltenes and resins) in the coke mass normally leaves additionalvoids in the coke mass. In turn, any further polymerization andcross-linking of the remaining coke mass often becomes more optimal dueto a lower asphaltene/resins to aromatics ratio. After cooling, the petcoke typically has greater internal surface area, with significantlymore micropores and mesopores. The increased carbon adsorption charactercan improve fuel properties via better adsorption of VCMs, sulfurreagents, etc. With sufficient cracking and hydrogenation of the cokemass, the resulting pet coke can also provide sufficient carbonadsorption character for treatment applications similar to traditionalactivated carbon.

[0767] Alternatively, additional hydrotreating of distillates can beachieved before quench and coke cooling, if sufficient time is allottedfor semi-continuous process cycles (i.e. batch process). That is,distillates can be added with excess hydrogen while the temperature andpressure of the coke are still sufficient for hydroconversion (e.g.hydrotreating). The distillates can be recycled through the coke bedwith excess hydrogen until sufficient hydroconversion has occurred. Thetypes of distillates include, but should not be limited to various gasoils, middle distillates, and naphthas. Preferably, the distillates,such as coker gas oils, can come directly from the coke fractionationunit, eliminating the need for substantial heating to reactiontemperatures. Depending on solvent action of the distillate, additionalseparation may be necessary in some cases to remove excess asphaltenes,resins, and heavy aromatics solutized from pet coke mass.

[0768] The above theory of operation generally applies to thehydroprocessing of pet coke. However, this theory of operation may notaccurately describe all applications. Therefore, this theory ofoperation should not limit the current invention, and should be used asa guide for ones skilled in the art to modify this technology forspecific applications.

[0769] In this manner, the hydroprocessing of pet coke can be generallyachieved with the proper catalysts. As with other hydroprocessingtechnologies the catalysts are tailor-made for the feedstock (e.g. cokemass characteristics), process operating conditions, and conversionlevels desired. One skilled in the art can make the necessaryadjustments in catalyst (type, character, and quantity) and operatingconditions, based on engineering calculations, and minor tests, ifnecessary.

[0770] (3) Exemplary Embodiment: Coke Hydroprocessing:

[0771] In an exemplary embodiment, process options of the currentinvention are used to substantially decrease overall coke yield andproduce a petroleum coke with adsorption characteristics approachingtraditional activated carbons of high quality. A third coke drum isadded to the traditional coke drum pairs of traditional prior art (i.e.groups of 3 vs. 2). A third coking cycle is also added. The three cyclesbecome coking, coke hydroprocessing, and decoking. In the coking cycle,the adsorption character of the petroleum coke is substantiallyincreased via process options of the current invention. In the cokehydroprocessing cycle, initial coke cooling is followed by simultaneoushydrogenation and cracking of the coke mass, which proceeds withsufficient residence time to obtain the desired conversion. Theremaining hydroprocessing cycle time is used for further cooling of thepetroleum coke with traditional coke quench media. In the decokingcycle, the coke quench is completed and traditional decoking cycle tasks(coke cutting, reheat, etc.) are accomplished.

[0772] Equipment modifications of delayed coking processes include, butshould not be limited to:

[0773] 1. Addition of a third coke drum; Preferably 3 new coke drumsw/higher pressure limits

[0774] 2. Hydrogen; addition/recycling system

[0775] 3. Catalyst additives; storage & injection system

[0776] 4. Associated piping, instrumentation, & controls

[0777] The primary process modifications involve the addition of thethird process cycle and the modifications & redistribution of processtasks. The primary purpose of the third process cycle is to providesufficient residence time for the coke hydroprocessing step. Byincorporating tasks of the traditional decoking cycle, this cokehydroprocessing cycle also allows potential increase in coker capacityvia reduction in coking cycle time. That is, the heater section becomesthe limiting factor in reducing cycle times. Though the overall cokercycle time increases, the cycle time to fill each coke drum can bereduced, increasing coker capacity. For example, a coker with currentcycle time of 14 hours has an overall coker cycle of 28 hours. Incontrast, the third coker process cycle can effectively reduce theindividual cycle times to 12 hours, but extend the overall coker cycleto 36 hours. However, one coke drum (of the same size or larger) isfilled every 12 hours, instead of 14 hours, increasing the cokecapacity.

[0778] In the coking cycle, the adsorption character of the petroleumcoke is typically increased to improve coke mass reactivity. Thisobjective can be usually achieved by the use of previously discussedprocess options of the current invention. These process options includelower heater outlet temperature, lower recycle rate, higher drumpressure, and/or modified coker feed with higher aromatics content. Inthis manner, the ratio of asphaltenes/resins to aromatics is low enoughto consistently produce highly porous sponge coke or honeycombcrystalline structure. These high porosity, coke crystalline structuresprovide sufficient solidification of coke mass and adsorption characterto improve coke mass reactivity. In addition, the lower heater outlettemperature, lower recycle rates, and lower coke density (i.e. less cokeper coking cycle) reduce the heater section limitations and increasecoke drum fill rates. This allows potential reduction in coking cycletime (e.g. 12 hours) and increases in coker capacity.

[0779] In the coke hydroprocessing cycle, initial pet coke cooling,hydrogen/catalyst addition, pet coke hydroprocessing, and further petcoke cooling occur. The initial pet coke cooling provides (1) optimalreaction temperature, (2) increased coke mass solidification, and (3)the means to inject hydrogenation catalyst additives, if necessary. Asnoted previously, the optimal temperature and pressure depend onsite-specific factors, including the coke mass composition & structureand hydroprocessing objectives. In many cases, the optimal temperaturefor coke hydroprocessing is normally 500 to 950° F. (preferably 700 to800° F.) and pressures of 15 to 2000 psig (preferably 15 to 100 psig).Secondly, the lower temperature (vs. 800 to 850° F.) also increases thesolidified coke content of the semi-solid coke mass. As discussedpreviously (i.e. theory of operation), the highly porous, solidifiedcoke in the semi-solid, coke mass provides the carbon adsorptioncharacter that increases the availability of the hydrogen free radicalions in predominantly solid-gas phase reactions. Finally, the initialcoke cooling can provide the means to add hydrogenation catalystadditives, such as iron oxides and/or iron sulfates. Traditional cokecooling media (e.g. steam, water, & sludges) can be used to attain theoptimal temperature. Various catalyst additives can be injected withthese media, particularly aqueous sludges, but other options may bepreferable to achieve better control and more uniform distribution inthe coke. One alternative would include the use of a coker fractionatorslipstream to serve as both carrier fluid and cooling medium. Thisslipstream (e.g. light coker gas oil or heavy naphtha) would preferablyvaporize at temperatures below the optimal hydroprocessing reactiontemperature. The catalyst additive(s) (e.g. iron oxide waste sludges)would be mixed with carrier oil/distillate prior to injection. Thevaporization of the carrier oil/distillate would provide the desiredcooling (with better control than water expanding to steam) and leavethe catalyst additives uniformly deposited on the pet coke surfaces.This would be similar to the deposition of SOx sorbents discussed later.The vaporized carrier oil/distillate would be recovered. One skilled inthe art could readily design and implement such a system addressingsite-specific needs and concerns. This initial coke cooling typicallyrequires 2 to 3 hours of coke hydroprocessing cycle time.

[0780] Initial hydrogen addition can be injected with the cooling media,the bulk of the hydrogen is added after the optimal temperature isreached. As the hydrogen is added to the coke drum, the system pressureis allowed to increase to the practical pressure limits of the cokedrums. For existing coke drums, this pressure limit is typically 80-100psig. A circulation rate of excess hydrogen is established with 1.5 to 8times (preferably 3-4 times) the hydrogen required for conversion. Thisexcess hydrogen circulation provides the means to remove gaseousreaction products (e.g. hydrogen sulfide, ammonia, water, etc.) forfurther processing and recovery of vaporized hydrocarbons. The hydrogenis recovered and recycled. Based on experience in other hydroconversionprocesses, one skilled in the art can design and implement a hydrogencirculation and product recovery system, which addresses site-specificfactors and concerns. Establishing hydrogen circulation and higher drumpressure can normally be achieved within 2 hours (preferably <1 hour) ofcycle time.

[0781] Simultaneous hydrogenation and cracking of the coke mass areinitiated and proceed with sufficient residence time to obtain thedesired conversion. As the hydrogen enters the system, the very porous,solidified coke within the coke mass (and its increased adsorptioncharacter in this exemplary embodiment) convert the molecular hydrogento free radical ions without catalyst additives. As discussedpreviously, the adsorption character of the coke mass and the solid-gasphase nature of coke hydroprocessing make the hydrogen free radicalsreadily available for migration to the reaction sites without excessivehydrogen partial pressure. The reaction sites are normally the surfaceof the reactants (e.g. asphaltenes, resins, & condensed aromatics). Thehigh concentrations of both reactive molecules and hydrogen freeradicals create driving forces for high degrees of complementaryhydrogenation and cracking reactions. Normally, the hydrogenation andcracking reactions preferentially attack the weaker bonds of theasphaltenes and resins. Significant breakdown and removal of complexaromatic compounds (preferably asphaltenes and resins) from the cokemass create additional voids in the coke crystalline structure. The sizeof these voids range form <2 nanometers to >50 nanometers. As a result,additional micropores, mesopores and macropores are created. This isanalogous to the removal of basal planes in the steam activation ofcarbonized carbons to produce high-quality activated carbons. Ampleresidence time of the exemplary embodiment allows lower operationaltemperatures that favor greater aromatic saturation. The third coke drumand third coker operational cycle of the exemplary embodiment provideample residence time of at least 3-12; preferably 4-6 hours.

[0782] The remaining hydroprocessing cycle time is used for furthercooling of the petroleum coke with traditional coke quench media. Whenthe coke hydroprocessing has achieved the desired conversion level, thepet coke is steamed out and cooled further for cutting from the cokedrum. Similar to delayed coking of the prior art, the petroleum coke iscooled to a temperature sufficiently low (e.g. 200° F.) to safely removethe pet coke form the coke drum. However, the remaining cokehydroprocessing cycle time (e.g. 2-3 hours) can be effectively used toreduce the rate of cooling and reduce thermal stress in the coke drums.As a result, all tasks of the coke hydroprocessing can be readilycompleted within a 12-hour cycle time.

[0783] In the decoking cycle, traditional decoking cycle tasks can bereadily accomplished within a 16-hour (preferably 12-hour) cycle timewith less thermal stress on the coke drums and less safety concerns.First, substantial cooling (e.g. 3-6 hours at reduced cooling rates) hasalready occurred in the coke hydroprocessing cycle. Consequently, cokecooling can often be completed within the first 2-3 hours. The next 6-8hours are available for draining, unheading, decoking, head-up, andtesting. The remaining cycle time (e.g. 2-3 hours) can be effectivelyused for warming up the drum at a lower rate, reducing thermal stressesin the coke drums. One skilled in the art of delayed coking candetermine the optimal use of cycle time for the different tasks. Theproper allocation of decoking cycle time can depend on site-specificfactors, including various safety concerns, coke drum conditions, cokecutting design & controls, and coke transfer facilities.

[0784] The primary results of the exemplary embodiment include (1)substantial reduction in overall coke yields, (2) significantimprovement in pet coke adsorption quality, (3) removal of cokeimpurities, and (4) higher coker capacity via reduction in cycle time ofindividual cycles, particularly coking cycle. The purpose and benefitsof the exemplary embodiment can be illustrated by the following example.A delayed coker currently has a coke yield of 33% and coking cycle timeof 16 hours. A fuel-grade, petroleum coke is produced with shot cokecrystalline structure, 10% VCM, and an in-drum density of 0.98 g/cc.With an exemplary embodiment coking cycle of 12 hours, the modifiedoperating conditions produce a highly porous coke with honeycombcrystalline structure to promote the coke hydroprocessing. This coke hasan in-drum density of 0.86 g/cc and roughly 22% VCM. The coke yield isincreased to approximately 37%. With a 25% hydroprocessing conversion,the overall coke yield is reduced to 28% and the modified petroleum cokeis similar in quality to medium grades of traditional activated carbons.By increasing the hydroprocessing conversion to 35%, the overall cokeyield is reduced to 24% and the modified pet coke approaches the qualityof premium activated carbons. Obviously, the lafter scenario is moredesirable with an effective reduction in overall coke yield of 9 wt. %(i.e. 33%-24%), primarily conversion to cracked liquids during the cokehydroprocessing. In addition, the cycle times have been reduced to thelowest practical levels: 12 hours. Though the increase in coker capacitywould appear to be 33% (i.e. 16/14), the change in coke densitiesreduces the weight of coke in each coking cycle by 14%. Thus, the netincrease in coker capacity would be roughly 19%. Even if the cokingcycle time can only be reduced by 2 hours, the higher drum fill rate cancover the change in coke densities and still increase coker capacity by0.3%.

[0785] One skilled in the art can make proper equipment and operationalmodifications to achieve the desired objective at site-specificapplication of this technology. As discussed previously, the applicationof the current invention can vary due to site specific factors,including existing coker design and operation, coker feeds, coke masscomposition, hydroprocessing objectives, and use(s) of the modifiedpetroleum coke.

[0786] (4) Other Embodiments: Coke Hydroprocessing

[0787] 1. This method can be performed without coke crystallinemodification of the current invention. some cokers won't need (e.g.sweet crude refineries)

[0788] 2. Lower coke hydroprocessing reaction temperature (e.g. 500-700°F; preferably 600-700° F.): Hydrogenation reaction equilibrium favorslow temp; residence time/reaction rate trade-offs

[0789] 3. Reduce conversion; Maximize profitability: Adsorption cokehigher value vs. cracked liquids

[0790] 4. Reduce conversion for fuel grade pet coke applications: Boiler& MHD Technology

[0791] 5. Use remaining cycle time for additional hydrotreatingcapacity: Gas oils, naphthas, etc.

[0792] 6. Add other additives to improve catalyst activity;

[0793] 7. New coke drums/reaction vessels designed for higher processand hydrogen partial pressures

[0794] New alloy clad drums w/latest technology; repetitive seals &press effects/thermal cycles

[0795] 8. Add other process options of current invention:Plastics/Rubber, Mod Drill Stem, etc.

[0796] Coke Fuel Product: SOx sorbents, VCMs, oxygen, ionizationchemicals

[0797] Coke Adsorption product: Chemisorption, other adsorptionenhancing additives

[0798] Add oxygen, nitrogen, and/or halogen surface groups or complexesto enhance adsorption character & chemisorption properties for specificadsorption applications

[0799] During this coke quench, chemisorption or other additives (e.g.sulfur) can be uniformly impregnated on the pet coke's adsorption carbonsurface via process options of the current invention.

[0800] Modified coke drum skirt to allow cutting of large honeycombchunks: low Press D

[0801] 9. Part of coke to MHD Cogeneration (e.g. on-site) & Remainder toadsorption uses

[0802] 10. 2-Stage thermal process: 700-750° F. for aromatic saturation;then raise temperature for thermal/catalytic cracking to 800-900° F:Alternate for prescribed periods of time in pet coke hydroprocessingcycle of modified delayed coking process.

[0803] 11. Carrier fluids (liquid and/or gas) can also be preferable toimprove reactivity and overall benefits; Use of various hydrocarbons forincremental hydrotreating/hydrocracking capacity in refinery w/lowseverity requirements; gas oils or FCCU slurry oil as carrier for H2 &Fe for hydrocracking in pet coke

[0804] 12. Reduce overall process coke yield via cracking &hydrogenation of coke compounds

[0805] 13. Reduce sulfur, nitrogen, and metals contents of the modifiedpetroleum coke: H2: hydrotreat liquid/coke mass to remove any exposed S,N, and the metals before coke crystal growth

[0806] 14. Reduce coke yield & improve coke qualities via optimized cokecondensation: addition of hydrogen: promote stabilization of cokecrystals

[0807] 15. Improve carbon adsorption character; approaching activatedcarbon applications: H2: lowest molecular weight gas promotesmicro-pores and mesopores; H2: stabilize coke crystals by saturating andhelp cross-linking; eliminate pitch like material, & promote crystalgrowth

[0808] 16. Densities of Desired Activated carbon quality used as basisfor degree of conversion or maximum conversion of pet coke and acceptwhatever quality of pet coke at end

[0809] 17. Incremental hydroprocessing capacity and/or additional gasoil production from lower heater outlet temperature: excess gas oil canbe pumped to the 3rd coke drum for hydrocracking coke in presence ofhydrogen, iron, and gas oil

[0810] 18. Variations among refineries due to trade-offs: technical &economical; One skilled in the prior art can.

[0811] (5) Overall Results

[0812] 1. Operate coking cycle at lower temperatures to assuresufficiently porous, sponge coke

[0813] 2. Reduce coking cycle time to limits of heater section: e.g. 12hours

[0814] 3. Cool coke to 600-750° F. with coker gas oil sidestream and addcatalyst additive, if needed

[0815] 4. If cycle time is sufficient (e.g., about 3-4 Hr.), additionalhydrotreating capacity (e.g. coker gas oils)

[0816] 5. Incorporate initial cooling in hydroprocessing cycle time(e.g., 3-4 Hr.)

[0817] 6. Finish cooling in decoking cycle, integrating desired cokeadditives and properties

[0818] 7. Reduce all cycle times to lowest practical levels: Increasecoker capacity & liquid yields

[0819] 8. Design pet coke magnetohydrodynamic cogeneration; Refinerypower and steam production

[0820] 9. Substantially increase refinery efficiency (e.g. >90%); ReduceCO2 & global warming

[0821] 10. Excess refinery gas to natural gas & plastics production;

[0822] 11. Excess coke to carbon adsorption applications (not floodingmarket; moderate price)

[0823] E. Pet Coke Activation: Chemical Extraction

[0824] A method for activation of petroleum coke for use in carbonadsorption applications was discussed in coke hydroprocessing process ofthe current invention. Certain types of chemical extraction werediscovered as an alternative method for pet coke activation. The methodsof chemical extraction are briefly described below.

[0825] The chemical extraction methods that activate the pet coke targetthe removal of the asphaltenes and resins form the coke mass in thedelayed coking process. Tetrahydrofuran (THF) or similar solvents can beused in the decoking cycle to extract the undesirable asphaltenes andresins. Asphaltenes and resins are normally soluble in THF, but mostcoke solids are not. Thus, washing or soaking the pet coke in liquid THFfor a sufficient period of time can be effective in removing theasphaltenes and resins. The removal of the asphaltenes and resinscreates voids of various sizes in the pet coke: macropores, mesopores, &micropores. The quality or grade of the adsorption carbon will bedetermined by the distribution of the pores in the resultant pet coke.This pore distribution can depend on various factors, including but notlimited to (1) initial coke crystalline structure, (2) localizedconcentrations of asphaltenes/resins, (3) extent of physical & chemicalattachment to coke structure, and (4) the degree of extraction.

[0826] An exemplary embodiment for this chemical extraction method wouldextract the asphaltenes and resins in the decoking cycle of the delayedcoking process. In the decoking cycle, the coke mass is cooled to atemperature sufficiently low and/or pressure is increased sufficientlyto maintain THF as a liquid. For example, the coke is traditionallycooled to 200° F. prior to draining, deheading, and cutting. The drumpressure may have to be maintained >30 psig to assure liquid THF (i.e.B.P=152° F. at 14.7 psig) during extraction. Once quench media isdrained and the desired operating conditions are established, liquid THFis injected into the coke mass until the coke drum is full. Aftersufficient residence time to allow appropriate solvent activity the THFextract is drained. This step can be repeated, if necessary to achievethe desired degree of extraction. After the extraction is complete, thesolvent extract is drained into a THF recovery system. After the THFextract is drained, the drum pressure is reduced and the remaining THFis vaporized. If needed, low-pressure steam is swept through the coke toremove any residual THF held by adsorption forces. Both the vaporizedTHF and steam are piped to the THF recovery system. In the THF recoverysystem, the liquid THF in the extract is vaporized in a flash separatorat sufficiently low pressures. The design of the THF separator wouldprovide means to readily remove the precipitated asphaltenes and resins.The vaporized THF is treated, if necessary, and recycled for the nextdrum of coke. Make-up THF is added, as needed.

[0827] Other embodiments of this chemical extraction method wouldinclude the following:

[0828] 1. Other solvents that have preferable solvent properties,physical properties and/or costs; For example: 2-methyl-THF has a highernormal boiling point of 250° F.

[0829] 2. This method of chemical extraction can be performed in vesselsexternal to coking process.

[0830] 3. This method of chemical extraction can be performed in a 3drum coker with 3d cycle.

[0831] 4. This method can be used in conjunction with cokehydroprocessing of the current invention.

[0832] 5. This method can be performed without coke crystallinemodification of the current invention.

[0833] 6. Reduced pressure vaporization of the solvent can be used. tofurther cool the pet coke.

[0834] F. Chemical Activation of Pet Coke for Carbon Adsorption

[0835] Methods for activation of petroleum coke for use in carbonadsorption applications were discussed in coke hydroprocessing andchemical extraction sections of the current invention. It has beenfurther discovered that the pet coke can be chemically activated for usein carbon adsorption applications. The methods of chemical activationare briefly described below.

[0836] The prior art of traditional chemical activation for activatedcarbons uses various chemicals to develop pores in carbonaceousmaterials. Chemical activation normally involves the followingmechanisms: (1) chemical decomposition of certain parts of thecarbonaceous material (e.g. cellulosic content of peat or wood), and/or(2) chemical support that does not allow resulting char to shrink duringcarbonization. The result is a very porous carbon structure that isfilled with activation agent. The activation agent is typically washedfrom the carbon and recycled. The two most common activation agents incommercial use are dehydrating agents: zinc chloride and phosphoricacid. Many other chemicals have been noted to activate carbonaceousmaterials, but only two others have been used commercially: sulfuricacid and potassium sulfide. A standard Oil process using anhydrouspotassium hydroxide is operated on a semi-commercial scale.

[0837] In the past, petroleum coke has had limited success as acarbonaceous raw material for the production of activated adsorptioncarbon. However, the modified crystalline structure of the currentinvention provides a much better starting material than traditionalpetroleum coke. Chemical activation of the modified coke of the currentinvention can be performed within the coking unit or separately.Preferably, the chemical activation occurs in the decoking cycle of thedelayed coking process. Essentially, the optimal activation chemical isadded to the porous sponge (or honeycomb) coke until the existing voidsare filled. Soaking the modified coke for sufficient residence time atsufficient temperature decomposes certain coke materials (preferablyasphaltenes and resins), leaving additional voids or pores in the coke.The quantity and types of pores (i.e. macropores, mesopores, and/ormicropores) can be controlled to a certain extent, producing low tomedium quality adsorption carbons at lower costs. In some cases,additional porosity and adsorption quality can be achieved by leavingthe activation agent in the pet coke, followed by further carbonizationin the proper furnace (e.g. rotary kiln). However, the additional costsare often not justified.

[0838] An exemplary embodiment for chemical activation in the currentinvention uses molten anhydrous potassium hydroxide in the delayedcoking unit. Preferably, the modified pet coke of the current inventionis created in the coking cycle via optimization of the cracking andcoking reactions. Using this very porous pet coke as the starting rawmaterial helps (1) improve the effectiveness of the molten anhydrouspotassium hydroxide and (2) provides better quality adsorption carbonproducts. At the beginning of the decoking cycle, the modified pet cokemass is a semi-solid at a temperature of about 750-850° F. and pressuresof 15 to 50 psig. As discussed in coke hydroprocessing, the solidifiedportion of the coke mass demonstrates a significant degree of carbonadsorption character. Molten anhydrous potassium hydroxide (M.P.=680°F.) is added to the coke mass until the voids are essentially filled (orless depending on desired conversion levels). The quantity of potassiumhydroxide in an exemplary embodiment may be 10 to 150 wt. % (preferably40-80 wt. %) of the initial coke weight. After sufficient residence time0.25 to 6 hours (preferably 0.5-2 hours), the potassium hydroxide (KOH)and reaction products are drained to the KOH recovery system. Theresidual KOH is stripped form the pet coke by steam and sent to the KOHrecovery system. The KOH recovery system separates the potassiumhydroxide from the reaction products and recycles the activation agent(KOH). The pet coke is further cooled and cut from the drums asdescribed in the current invention.

[0839] Other embodiments of this chemical extraction method wouldinclude the following:

[0840] 1. Treat modified pet coke with phosphoric acid and/or steam;750-1110° F. in rotary kiln.

[0841] 2. Pyrolysis oxidation of modified pet coke; followed bytreatment with nitric acid.

[0842] 3. Other activation agents with preferable chemical properties,physical properties, and/or costs.

[0843] 6. Uses of Improved Pet Coke Adsorption Characteristics.

[0844] The improved adsorption characteristics of the modified coke inthe current invention provide greater opportunity to further enhance itsfuel qualities and carbon adsorption properties. Various adsorption andimpregnation techniques can uniformly add various chemical agents to theinternal pores of the modified pet coke. These chemical agents can beused to (1) reduce sulfur oxide emissions from the pet coke combustion,(2) improve combustion characteristics of the modified pet coke, and (3)enhance carbon adsorption characteristics for use of the modified petcoke in various carbon adsorption and catalyst applications. These sameadsorption and impregnation techniques could also be applied tounmodified pet coke (e.g. anode-grade sponge coke from sweeter crudes).However, the success of such applications can be limited due to lesscarbon adsorption character. In addition, these adsorption andimpregnation techniques can also be applied to other porous,carbonaceous materials. Greater success (vs. unmodified pet coke) can beattainable, particularly with activated carbon materials or carbon-basedcatalysts.

[0845] A. Coke Adsorption and/or Impregnation with Sulfur Reagents

[0846] As noted earlier, certain chemical agents can be uniformly addedto the petroleum coke to mitigate the problems associated with highsulfur levels in the modified petroleum coke. These impregnated chemicalagents (e.g. sorbents) scavenge the coke sulfur in the combustionprocess and convert the sulfur to sulfur compounds, which are solidparticulates at the flue gas temperature of particulate control devices(i.e. existing or otherwise). In this manner, the fuel's sulfur can becollected in innocuous sulfur compounds in the combustion systems'existing (or modified or new) particulate control device, instead ofbeing emitted to the atmosphere as sulfur oxides (SOx). The conversionof sulfur oxides to particulates that are collectible in the existingparticulate control device is similar to dry sorbent scrubbingtechnology (prior art). On the other hand, the integration of chemicalagents, such as SOx sorbents, into the very porous crystalline structureof the modified coke is conceptually similar to the impregnation ofactivated carbon (prior art). However, this impregnation of the modifiedpet coke with sulfur reagents (present invention) is an unique processthat provides additional utility and benefits, including higher sulfurremoval efficiencies and/or more efficient sulfur reagent (e.g. SOxsorbent) utilization.

[0847] (1) Prior Art; Dry Scrubbing & Activated Carbon Impregnation

[0848] a. Dry Sorbent Scrubbing:

[0849] Various technologies have been developed to remove sulfur oxides(SOx) from combustion flue gases. The most common are wet and dryscrubbing technologies. Wet scrubbing technologies use liquids to absorbgaseous SOx and chemically convert them to compounds that can bephysically removed from the flue gas. In contrast, dry scrubbingtechnologies use solids to adsorb the gaseous SOx and chemically convertthem to particulate compounds that can be readily collected inparticulate control devices. The adsorbing solids are commonly referredto as sorbents. Dry scrubbing technologies are further classified by thetype of sorbent injection: solids (dry) or slurry (wet). The slurryinjection is currently capable of higher SOx removal efficiencies, butrequires higher reaction times at lower temperatures with higher capitaland operating costs. Sorbent injection of dry solids is the scrubbingtechnology that is most similar to the present invention, and isdiscussed below in greater detail.

[0850] Various chemical compounds containing alkali metals and alkalineearth metals (Periodic Table Groups IA and IIA) have been used as drysorbents to remove sulfur oxide emissions from the exhaust gas ofcombustion systems. Three primary types of dry sorbents are as follows:

[0851] 1. Calcined Lime (CaO) convert SOx to CaSO₄ at temperatures of1600-2300° F.

[0852] 2. Hydrated Lime (Ca(OH) 2) converts SO₂ to Ca SO₃ at <1020° Fdown to saturation.

[0853] 3. Sodium Carbonates convert SOx to Na₂SO₄ at temperatures of275-400° F.

[0854] Typically, the sulfur oxides (SOx) are first adsorbed and thenchemically converted to chemical compounds. The sulfur-bearing compoundis normally inorganic and a dry, particulate at the temperature of theparticulate control device. Thus, the sulfur bearing particulate iscollected and the sulfur oxide emissions are reduced. The overallreduction of sulfur oxide emissions is primarily dependent on (1)sorbent type and amount (i.e. sorbent stoichiometric ratios), (2)injection temperature and thermal profile of the combustion process, (3)sorbent calcine surface area, (4) sorbent particle size, (5) initial SOxlevel, and (6) associated reaction equilibrium and reaction kinetics,including associated limitations.

[0855] The following limitations often hinder favorable reactionkinetics (e.g. calcium sorbent):

[0856] 1 . Bulk diffusion of SOx to the sorbent particle (e.g. CaO)

[0857] 2. Diffusion of SOx through the pores of sorbent (e.g. CaO)

[0858] 3. Diffusion of SOx through the layer of converted sulfurcompound (e.g. CaSO₄)

[0859] 4. Filling of the small pores causing a decrease in reactive area

[0860] 5. Buildup of converted sulfur compound (e.g. CaSO₄) at poreentrances causing pore closures

[0861] 6. Loss of surface area due to sintering (i.e. high temperatureexposure)

[0862] 7. Reduced kinetic reaction rates at low temperatures

[0863] Consequently, equilibrium is seldom achieved and greaterstoichiometric ratios are required to overcome these limitations toachieve higher SOx removal efficiencies. Sorbent to sulfur ratios on theorder of 1.5-2.0 are usually required to achieve SOx removalefficiencies >50%.

[0864] The point(s) of sorbent injection is also a major factor indetermining SOx removal efficiency. As noted above, each type of sorbenthas an ideal temperature window to react with the sulfur oxides (i.e.SOx). As such, injection of the sorbent upstream of this temperaturewindow is necessary to allow ample mixing time and reaction time inthese temperature zones. For example, calcined lime (CaO), derived fromvarious possible sorbents, typically requires a temperature window about1600 to 2300 degrees Fahrenheit (° F.). Thus, injection in the furnaceis desirable. Injection temperatures typically range from 1800 to 2700°F. However, high flame temperatures, particularly at temperatures >2500°F., can sinter the sorbent's crystalline structure. Sintering normallydecreases reactive sorbent surface area and access to it. In fact,mixing pulverized, calcium sorbents (e.g. limestone) with solid fuelshas been tried with lower SOx removal effectiveness due to severesintering in the high temperature flame zones. Consequently, a separatesystem is normally required to inject SOx sorbents downstream of thehigh-temperature, flame zones. Unfortunately, more than one injectionpoint is often necessary to inject the sorbents into the propertemperature window for different boiler loads. That is, one injectionpoint often has significantly different temperatures for differentboiler loads, reducing sorbent effectiveness and average SOx removal.

[0865] b. Impregnation of Activated Carbon:

[0866] Activated carbons have been impregnated with various organic orinorganic chemicals for three primary reasons:

[0867] (1) Optimization of Existing Properties of Activated Carbon:Catalytic oxidation of organic and inorganic compounds is one example ofan existing property of activated carbon. Impregnation of the activatedcarbon with potassium iodide can promote additional/controlled oxidationand optimize this property. Other examples also exist.

[0868] (2) Synergism Between Activated Carbon and Impregnating Agent:Activated carbon and sulfur is one example of such synergistic effectsof the sulfur impregnating agent for the efficient removal of mercuryvapors from gases at low temperatures. Other types of synergism exist.

[0869] (3) Use of Activated Carbon as an Inert Carrier Material. Theimpregnation of phosphoric acid on activated carbon for ammonia removalis an example of activated carbon as an inert porous carrier material.In this case, the internal surface of the activated carbon adsorbs theammonia at certain reaction sites. The weak Van der Waals forces ofadsorption allow the ammonia molecules to migrate along the internalsurface of the carbon to the phosphoric acid's reaction sites. Theammonia then reacts with the phosphoric acid to form ammonium phosphate.This two-step reaction mechanism is commonly referred to aschemisorption.

[0870] The manufacture of impregnated activated carbons is achieved bytwo basic methods: soaking impregnation or spray impregnation. Soakingimpregnation consists of soaking an activated carbon of suitable qualitywith solutions of salts or other chemicals. In the spray impregnation,the suitable activated carbon is sprayed in a rotary kiln or in afluidized bed under defined conditions. In either case, the wet,impregnated activated carbon needs to be dried in an appropriate drier(e.g. rotary kiln or fluidized bed drier). In some applications, theimpregnating agents are present as hydroxides, carbonates, chromates,nitrates, or other complex ion forms. In these cases, the impregnatingagent must be subjected to thermal treatment at temperatures of 300 to400 OF to decompose the anions. After drying and/or otherpost-impregnation treatment steps, the desired impregnating agentremains on the internal surface of the activated carbon.

[0871] Limited and homogeneous distribution of the impregnating agentson the internal surface of an activated carbon is important. Inaddition, blocking of macropores, mesopores, and micropores should beavoided in order to keep the impregnation agent accessible for theadsorbed reactants. Though impregnation agents are typically up to 30wt. % of the impregnated activated carbon, the impregnating agent ispredominantly distributed in the micropore system with minimal poreblockage in many types of successful impregnation. For example,activated carbon has been successfully impregnated with 15 wt. % sulfurwith a fairly uniform distribution of sulfur in a monomolecular layer onthe internal surface of the activated carbon. The impregnation onlyreduced the micropore system's surface area from 742 to 579 m²/g. Inthis manner, the sulfur-impregnated activated carbon not only removesmercury via sulfur chemisorption, but also provides substantialadsorptive removal of other gas impurities. Similarly, other impregnatedactivated carbons can achieve limited, homogeneous distribution of up to30 wt. % impregnating agent, predominantly in the micropore system,without plugging vital passage ways throughout the activated carbon'spore systems.

[0872] (2) Present Invention; Adsorption/Impregnation of Modified PetCoke; Sulfur Reagents:

[0873] Unlike the prior art, the present invention incorporates sulfurreagents (e.g. sorbents) in the fuel, providing superior performance andsubstantial advantages over the prior art. That is, the presentinvention can integrate these various types of reagents for sulfurremoval within the porous crystalline structure of the modifiedpetroleum coke. In so doing, any sulfur reagents are generally shieldedfrom the high flame temperature (i.e. sintering) until the petroleumcoke char is oxidized. In this manner, the desired reagent crystallinestructure is maintained to achieve higher sulfur removal efficienciesand, in many cases, eliminate the need for a separate sorbent injectionsystem. Furthermore, the monomolecular to di- or tri-molecular layers ofsorbents are less prone to the detrimental effects of sintering due toless blockage of reactive sorbents with altered sorbent crystallinestructure. At the same time, several of the reaction kinetic limitationsof the prior art are substantially reduced to improve the sulfur removalefficiency and/or increase efficiencies of reagent utilization (i.e.lower stoichiometric ratios). The integration of these chemical reagentsinto the porous structure of the modified petroleum coke is the key.Similar to the soaking impregnation of activated carbon, the aqueouscoke quench solution carries the desired reagents into the macropores,mesopores, and micropores of the pet coke in the quench cycle of thecoking operation. This novel process of impregnating the highly porous,modified pet coke can be summarized in (1) selection of appropriatesulfur reagent(s), (2) preparation of the coke quench solution, (3)modification of quench cycle in coking operation, (4) impacts of petcoke pulverization, and (5) the performance of reagents in thecombustion of the modified pet coke.

[0874] a. Selection of Appropriate Sulfur Reagents:

[0875] The selection of optimal sulfur reagents (including traditionalSOx sorbents of the prior art) for a particular application is dependenton many factors; primarily reactivity, selectivity, temperaturesensitivity, resistance to sintering, solubility, and costs. As notedabove, traditional SOx sorbents are generally selected from the class ofinorganic compounds that contain alkali metals and/or alkaline earthmetals (Periodic Table Groups IA and IIA). However, the presentinvention should not be limited to these compounds, but also include anyother chemical compound that readily reacts with sulfur (with or withoutadsorption) and forms particulate compound(s) that is readily collectedfrom the flue gas stream.

[0876] Evaluation of the optimal sulfur reagent can vary significantlyfor each combustion application. The sulfur reagents' reactivity,selectivity, temperature sensitivity, and resistance to sintering allrelate to the reagent's ability to efficiently convert primarily sulfurto collectible compound(s). The reagent's effectiveness and desirabilitydepend on the required sulfur removal and the temperature profile undervarious loads for the specific combustion system. In many cases, thesulfur reagent's resistance to sintering is not a major factor due tothe coke char insulation of the reagent crystalline structure in thecurrent invention. However, this mechanism of sintering prevention, canvary substantially in different combustion applications due tofirebox/burner design and operation. That is, the need for timely cokechar burnout in firebox hot zones (e.g. >2300° F.) and the requiredparticle size distribution of the modified pet coke can make this moredifficult to achieve in some cases. Consequently, the reagent'sresistance to sintering can become a significant factor, consideringthis reagent injection in the fuel. However, as noted earlier, thedetrimental sintering effects are substantially reduced form the priorart due to the relatively minor thickness (i.e. layers with <5 sorbentmolecules thick; preferably I sorbent molecule thick) of the sorbentswithin the pet coke pores.

[0877] In addition, solubility characteristics and costs of differentsulfur reagents can also vary significantly for each refinery cokerapplication. The required solubility characteristics is dependent on thecoker's coke quench characteristics and process requirements. The costscan vary significantly with the required quantity of reagent for desiredsulfur removal and the required preparation of the coke quench solution.The delivered price of various reagents can vary, particularly inrelation to reagent source proximity and types of transportationavailable.

[0878] Overall, the preference rank of sulfur reagents is generally thesame among different applications. However, all of these factors canvary significantly for different applications, particularly cost.Consequently, these factors must be considered in each application, andthe optimal sulfur reagent selected accordingly. One skilled in the artcan evaluate these various factors to determine the optimal reagent fora particular application.

[0879] b. Preparation of Coke Quench Solution:

[0880] The preparation of coker quench solution primarily involves theaddition of the sulfur reagent of choice to the quench water of thecoking cycle. The water solubility of the chosen reagent is a primaryconsideration. For example, sulfur reagents containing alkali metals(Periodic Table Group IA) are generally highly soluble in water. Incontrast, sulfur reagents containing alkaline earth metals (PeriodicTable Group IIA) usually have limited solubility in water. Ideally, thedesired quantity of reagent (i.e. reagent/sulfur ratio) can be added tothe modified pet coke via a sub-saturated, saturated, or supersaturatedsolution of the reagent in the quench water. Alternatively, a saturatedsolution of reagent with suspended reagent solids in the quench watercan be used, as long as the reagent is pulverized to the smallestpractical size distribution (e.g. 95% <4 microns) feasible.

[0881] The coker reagent/quench solution primarily depends on therequired quantity of reagent to achieve the desired SOx removal, thereagent's solubility, and the quantity of quench solution required bycoker process needs. In most cases, keeping the quantity of quenchsolution relatively constant is desirable. In some cases, however,increasing the quantity of quench solution may be desirable to decreasethe required amount of suspended reagent solids in a saturated quenchsolution. One skilled in the art can readily determine the properquantity of reagent based on desired reagent/sulfur ratios. Furthermore,one skilled in the art can determine the desired quantity of quenchsolution based on coker process requirements, reagent solubility, andprocess equipment capabilities. In cases using saturated solutions withsuspended reagent solids, the reagent should be pulverized to the lowestpractical size distribution (e.g. <4 microns; preferably <2 microns) topromote integration into mesopores and macropores and minimize pluggingof pores. It should be noted that the quench solution in many cokersalready contain sludges from other refinery processes withoutsignificant plugging problems. These sludges often contain suspendedsolids with solid particles >75 microns (or micrometers).

[0882] c. Modification of Coker Quench Cycle:

[0883] The quench cycle of the coking operation provides the mechanismto impregnate the porous, modified pet coke with sulfur reagents.Whether saturated, supersaturated, sub-saturated, or saturated withsuspended reagent solids, the quench solution is pumped through thesolidifying coke mass in a manner that is very similar to the currentquench cycle. This quenching process forces the quench solution underhigh pressure through the internal pores of the modified pet coke, andprovides significant advantages over most methods used to impregnateactivated carbon. However, some slight modifications may be necessary toaccommodate any excessive suspended reagent solids and potential forplugging. One skilled in the art can determine the need formodifications of equipment or process parameters, based on equipment andprocess specifications.

[0884] As the quench solution passes through the hot, solidifying cokemass (temperatures>solution boiling point at process conditions), mostof the water in the aqueous quench solution evaporates and leaves thedesired reagent integrated in the pet cokes crystalline structure.Similar to crystallization from solutions, initial evaporation of thequench solution will create a supersaturated solution of the reagent.Nucleation (via coke crystals or otherwise) is expected to inducereagent crystal growth on the pet coke surface at a molecular scale(e.g. <2 nanometers). Similar to the impregnation of activated carbon,molecular layers of reagent can be uniformly deposited on a limitedamount of internal surface area (predominantly micropores). Thesemolecular layers are typically less than 5 reagent molecules thick(preferably 1 molecule thick). In this manner, the reagent can bedeposited somewhat uniformly in the macropores, mesopores, andpreferably micropores of the modified petroleum coke of the currentinvention. Again, by definition, these pores have the following roughdiameter sizes: macropores>50 nm (nanometers); mesopores=2 to 50 nm; andmicropores<2 nm.

[0885] A saturated solution (or slightly sub-saturated solution) ofsulfur reagent should be continually used for further cooling and cokecutting. After the coke has cooled sufficiently and quench waterevaporation no longer occurs (temperatures <solution boiling point atprocess conditions), the saturated (or sub-saturated) quench solutionfor further cooling avoids excessive leaching of the reagent from theinternal surface of the coke (i.e. reagent solubility in non-saturatedquench solution). For the same reason, a saturated solution (or slightlysub-saturated) should also be used for the cutting water that cuts thecoke from the coke drum.

[0886] After cutting the coke from the drum, some of the reagentsdeposited on the macropore walls will become part of the externalsurface of the coke chunks (preferably diameter=6-24 inches). Thispotentially exposes these reagents to weathering during transport. Theresistance to water flow through the internal pores at ambient,atmospheric conditions limits weathering effects to mostly the externalsurface. In contrast, most of the reagents deposited in micropores,mesopores, and some macropores will still be part of the internalsurface of the coke chunks. The proportion of each will depend on thecoke crystalline structure and the type/degree of coke cutting. That is,the internal surface area increases as the porosity of the sponge cokeincreases with predominantly micropores and mesopores. The greater theinternal surface area, the greater the protection of the reagent fromweathering and high flame temperatures (discussed later). This furtheremphasizes the utility of the process options of the current inventionfor increasing the pet coke porosity beyond traditional sponge cokeporosity, if necessary.

[0887] d. Impacts of Pet Coke Pulverization:

[0888] The pulverization of the modified pet coke can affect the reagentutilization. In many applications, the modified petroleum coke willnormally be pulverized at the end-user's facility immediately prior tocombustion. In these cases, additional reagent will normally be exposedto the flame zone on the external surface of the coke. The quantity ofreagent exposed in this manner is primarily dependent on the pet cokecrystalline structure and the type/degree of pulverization. As notedpreviously, the deposition of reagent is predominantly in the microporesin many cases (similar to impregnation of activated carbon). Also, thepet coke crystalline structure can be controlled, to a certain degree,by the process options of the current invention. The type and degree ofpulverization depends on the pulverizers and combustion requirements atthe end-user's facility. Again, as noted earlier, the detrimentalsintering effects are substantially reduced form the prior art due tothe relatively minor thickness (i.e. layers with <5 sorbent moleculesthick; preferably 1 sorbent molecule thick) of the sorbents within thepet coke pores.

[0889] For example, pulverization can range from >60 to >95% passingthrough 200 mesh (i.e. <75 microns), depending on the particle sizedistribution required to complete combustion before the furnace exit.This depends on the combustor's design and operation, the fuel mix, andthe combustion characteristics of the modified petroleum coke. Duringpulverization, some of the sulfur reagent may actually be separated fromthe modified pet coke, but most should remain with the fuel. In manycases, the molecular nature of the sulfur reagent will substantiallyreduce the impact of exposure to high flame temperatures in thecombustion process. That is, the detrimental effects of sintering aregreatly reduced because the amorphous crystalline layer of sinteringlimits access to only a few molecular layers, if at all. In contrast,sintering of larger particles (e.g. 1-40 microns) in the prior art canblock a much higher percentage of internal reactive surfaces of thelarger sorbent crystalline structures.

[0890] e. Performance of Reagents in the Combustion of the Modified PetCoke:

[0891] During the combustion of the modified pet coke, the sulfurreagents in the coke crystalline structure react with the fuel sulfur ina manner that normally increases the prior art's SOx reduction for agiven sulfur reagent/sulfur ratio. The improved performance isattributed to a combination of factors, including (1) reduced sinteringeffects, (2) improved reaction mechanisms, and/or (3) reduced kineticreaction limitations (vs. the dry sorbent scrubbing of the prior art).

[0892] As noted in the prior art discussion, sintering is a primarycause for the reduction of SOx removal and sorbent utilizationefficiencies in the prior art. That is, sintering effectively changesthe sorbent crystalline structure, reducing porosity and adsorptioneffectiveness. With the present invention, the impact of sintering ismitigated by the following primary mechanisms:

[0893] (1) Sulfur reagents can be effectively insulated from the hotflame by the shelter of the surrounding pet coke char (i.e. minimalthermal conductivity or high insulating properties of covalent bondedmaterials such as polymeric hydrocarbon structure of pet coke char). Formost of the reagent on the internal pores of the char, this sinteringprotection is provided until downstream of the primary flame, where thepet coke char is oxidized and consumed at flue gas temperatures of1600-2800° F, (preferably 2100-2300° F.). That is, the devolatilizationand the primary flame zone typically occur in the first 0.01 to 0.10seconds. In contrast, the char usually is oxidized and consumed after 1to 2 seconds. and/or

[0894] (2) The molecular nature of the sulfur reagent substantiallyreduces the detrimental effects of sintering. That is, access to manyreactive sorbent molecules deep inside a large crystalline structure(1-40 microns) are inhibited by sintering in the prior art. In contrast,the molecular nature of the impregnated reagent of this invention (e.g.deposited in molecular layers <2 nanometers) severely limits the loss ofaccess to reactive sulfur reagents due to sintering.

[0895] With limited impact from sintering, the reactive reagents aremore effectively utilized in the conversion of fuel sulfur to sulfurcompounds that are collectible in particulate control devices.Consequently, sulfur conversion will depend more heavily on thedecomposition or breakdown rate of sulfur compounds within the coke.

[0896] The sulfur in the petroleum coke is primarily tied up asthiophenes in heavy hydrocarbons (e.g. aromatics, asphaltenes, andresins) of the coke char. As temperatures of the coke char exceed 1000°F., the heavy hydrocarbons thermally crack and release sulfur from tightchemical bonds. The resulting sulfur (or sulfur compound) tends tooxidize before the fixed carbon of the coke char. Thus, gaseous sulfuroxides are typically formed prior to the complete oxidation of the char.In addition, the thermal cracking and volatilization of the low-qualityVCMs (i.e. boiling points >750° F.) in the modified coke of the currentinvention is expected to provide greater mass transfer in the internalpores and expose reagent layers on the pet coke's surface. Again, VCMsare Volatile Combustible Materials as defined by ASTM Method D 3175. Asa result, sulfur adsorption and conversion can be achieved by variousmechanisms, including:

[0897] (1) Oxidation of coke sulfur compounds to gaseous sulfur oxidesthat migrate to the adjacent reagent molecules. SOx adsorbed by reagentmolecule and SOx chemically converted. Adsorption can take place eitherwithin or outside the pet coke particles or char.

[0898] (2) Similar to chemisorption associated with impregnatedactivated carbon, the gaseous sulfur oxides from oxidation of cokesulfur compounds are adsorbed by the coke crystalline structure andchemically converted by the sulfur reagent: via migration to reactionsites.

[0899] (3) Sulfur compounds (not in traditional oxide form) are releasedfrom the breakdown of the coke sulfur compounds. These sulfur compoundsare adsorbed by the pet coke crystalline structure and chemicallyconverted by the sulfur reagent. This mechanism is more likely withnon-traditional reagents that react with non-oxide forms of sulfur.And/or

[0900] (4) As the char of the modified coke is oxidized/consumed attemperatures of 1450-2000° F., unreacted reagent is released from thecoke with substantially less sintering (vs. limestone or lime mixed withfuel). This unreacted reagent adsorbs and converts sulfur oxides (fromcoke or other fuels) in a manner similar to traditional dry sorbentinjection of the prior art.

[0901] In this manner, the present invention not only reduces the impactof sintering on sulfur reagents in the furnace, but provides alternativemechanisms of adsorption and chemical conversion to achieve the desiredSOx removal efficiencies.

[0902] The present invention also substantially reduces several of thekinetic reaction limitations for the sulfur sorbents described in theprior art: dry sorbent scrubbing:

[0903] (1) Bulk diffusion of SOx to the reagent as a reaction constraintis greatly reduced. The reactive sulfur reagents are contained in thepet coke crystalline structure, surrounded by or adjacent to the area ofhighest sulfur concentration: the pet coke itself. Regardless of theadsorption and chemical conversion mechanism, the sulfur and reagent arein close proximity.

[0904] (2) In general, sulfur reagents of this invention havesubstantially smaller particle size distribution (e.g. diameters <2nanometers vs. <1-40 micrometers). Thus, kinetic reaction limitations2.-5. (described in prior art: dry sorbent scrubbing) become far lesssignificant. That is, the very small reagent particles substantiallyreduce the ratio of sulfur molecules adsorbed per reagent particle,mitigating concerns of sulfate layers and pore pluggage.

[0905] (3) Sulfur reagents of the current invention are activated and/orreleased in a reactive form well ahead of the desired temperature windowfor reagent adsorption and chemical conversion of sulfur compounds (e.g.sulfur oxides).

[0906] For a given application, the performance of the sulfur reagents(or sorbents) in the combustion of the modified pet coke issignificantly improved due to any one, a combination, or all of thesefactors. Also, the performance of the sulfur reagents can be furtheroptimized by controlling the pet coke char burnout and the availabilityof the sulfur reagents. In turn, the char burnout and availability ofthe sulfur reagent can be controlled, to a certain degree, by the cokeparticle size distribution, VCM quality, and VCM content of the modifiedpet coke. The current invention should not be limited by the foregoingtheories of mechanisms and operability, but be used as the bases foroptimizing the technology for different types of applications.

[0907] The process options to increase sponge coke porosity and VCMsbeyond traditional sponge coke become more important to optimize thebalance between improving combustion characteristics and achievingadequate SOx removal. In many cases, these features will remaincongruent and work together. In other cases, however, these features ofthis invention need to be optimized to strike a realistic balance forthe individual applications of this technology. Thus, the currentinvention should not be limited by the general theories exposed herein,but encompass the practical application of this technology to theindividual circumstances of each situation. That is, the generaltheories can be used as a guide, but may not specifically apply to allapplications. One skilled in the art can modify the coker process tooptimize this technology for each application and remain in the spiritand intent of the current invention.

[0908] (3) Exemplary Embodiment; Sox Sorbent=Calcitic Hydrated Lime:

[0909] In an exemplary embodiment, calcitic hydrate (alias calcitichydrated lime, high calcium hydrated lime, or calcium hydroxide Ca(OH)₂)is impregnated on the porous pet coke. This exemplary embodiment canbest be summarized by again reviewing (1) selection of desired sulfurreagent (e.g., calcitic hydrate), (2) preparation of the quenchsolution, (3) modification of quench cycle in the coking operation, (4)pulverization of the pet coke fuel, and (5) performance of the calcitichydrate in the combustion of the modified pet coke.

[0910] a. Selection of Calcitic Hydrate as Sulfur Reagent:

[0911] In general, calcitic hydrate may be selected as the mostdesirable sulfur reagent, primarily due to its low costs, reactiontemperature window, high reactivity, and resistance to sintering. Inthis invention, reagents with alkaline earth metals (Periodic TableGroup IA) may be preferable to reagents with alkali metals (PeriodicTable Group IIA) due to higher reaction temperature windows (800-2600°F. vs. 250-350° F, respectively). That is, alkali metal reagents addedto the modified pet coke may form less desirable compounds (e.g. sodiumvanadates) prior to reaching the proper temperature window in thecombustion system (i.e. downstream of the economizer). In contrast, thereagents with alkaline earth metals may be injected via the modified petcoke into their regions of greatest sulfur reactivity (furnace througheconomizer).

[0912] Calcium is generally the alkaline earth metal with the greatestsulfur reactivity and the lowest cost. Among the calcium reagents,hydrated limes (e.g. calcitic & dolomitic) have the highest SOx removalcapabilities, primarily due to higher specific surface areas (10-21 m²/gvs. <6 m²/g) than carbonate forms (e.g. limestone & dolomite). Infurnace zones exceeding 2000° F, calcitic hydrate (i.e. Ca(OH)₂) derivedfrom limestone generally calcines/dehydrates with a continual decreasein surface area; primarily due to sintering. With the reduced impact ofsintering in this invention, the calcitic hydrate has SOx removalcapabilities up to and sometimes exceeding 75% (vs. 60% in the priorart). In contrast, dolomitic hydrates (Ca(OH)₂ with MgO or Mg(OH)₂)calcine with a substantial increase in surface area in the prior art,and demonstrate higher SOx removal capabilities. As such, dolomitichydrates have a greater resistance to sintering. With the currentinvention, dolomitic hydrates have SOx removal capabilities up to 90%(vs. 75% in the prior art). However, the magnesium in the dolomitichydrates is usually chemically inert. Though it improves calciumutilization, the magnesium can detrimentally impact total ash loading,ash fouling characteristics, and ash reuse/disposal. In addition,dolomitic hydrates, particularly the often-preferred dihydrated form,has significantly higher costs (e.g. production & transportation). Oneskilled in the art can evaluate these various factors to determine theoptimal reagent for a particular application. In general, though,calcitic hydrate may be selected as the desired reagent due to lowercosts, related ash character & loading, solubility characteristics, andthe mitigation of sintering effects offered by this invention.Consequently, the remaining discussion of the exemplary embodiment willexamine the impregnation of calcitic hydrate on the pet coke.

[0913] b. Preparation of Coke Quench Solution:

[0914] The preparation of coker quench solution involves adequateaddition of calcitic hydrate to the quench water for the decoking cycle.This can be accomplished by various means, including (1) the directaddition of commercially available calcitic hydrate or (2) the additionof commercial calcitic lime (i.e. quick lime CaO) that partially orfully converts to the hydrated form. Commercial calcitic hydrate isnormally prepared from hydration of calcitic lime with particleagglomeration before shipment. Generally, the calcitic hydrate is 72-74wt. % calcium oxide (CaO) and 23-24 wt. % percent chemically combinedwater. Either approach can be accomplished on-site (i.e. at the coker)with additional equipment for storage, mixing, settling, etc. The latterapproach, completed on-site, may generally be preferred due to lowercosts, potential use of the high heat of solution, and the developmentof a finer crystalline structure. That is, the hydrated form of thesecond approach (e.g. without agglomeration) tends to have a crystallineform with finer particle size than typical commercial production ofcalcitic hydrate from quick lime. However, insufficient purity ofcalcitic hydrate (vs. a combination of calcitic hydrate and calciticlime) is a potential drawback of the second approach. However, in somecases, this combination can be preferable, if the calcitic lime isuniformly deposited on the pet coke internal pores without theadditional water of the hydrated form.

[0915] In either approach, the quench solution becomes a saturated orsub-saturated solution of calcitic hydrate (i.e. Ca(OH)₂) in water. Thesaturated solution is preferable (vs. suspended solids of pulverizedcalcitic hydrate) to maximize molecular deposition of calcitic hydratein the mesopores, macropores and preferably micropores of the modifiedpet coke and to greatly reduce pluggage of any pores. The saturatedquench solution can be used in the following cases: (1) low to mediumcoke sulfur levels (e.g. <4.0 wt. %), (2) low to medium SOx removalrequired (e.g. <50%), and/or (3) high water quench rates (e.g. >200gallons/ton of coke). Items (1) and (2) relate to the mass of calcitichydrate required (i.e. stoichiometric ratio of Ca/S required to achievea desired SOx removal level). The Ca/S ratio of the current inventionranges from 0.1 to 4.0 (preferably 0.5 to 2.0) to achieve SOx removallevels up to and exceeding 75%. Item (3) refers to the quantity ofquench water available to incorporate the required calcitic hydratewithin solubility limits (i.e. saturated or sub-saturated solution).Since the current invention promotes increasing coke VCM, water quenchrates can be increased by reducing quantities of steam at the beginningof the decoking cycle to strip out trapped hydrocarbon liquids andinitiate coke cooling.

[0916] For example, a coker currently produces 1000 ton/day of pet cokewith 4.0% sulfur. The utility boiler requires <50% reduction in the SOxof the pet coke portion of the coke/coal blend. If the Ca/Sstoichiometric ratio required to achieve this level is 1.5, the dailyamount of calcitic hydrate required in the pet coke is roughly 277,500pounds (1000×2000×0.04×74/32×1.5). At atmospheric pressure, thesolubility of calcitic hydrate in pure water is roughly 0.165 grams/ccat 20° C. and 0.077 g/cc at 100° C. This translates to approximately 1.4lb./gallon and 0.6 lb./gallon, respectively. The saturated quenchsolution that is totally evaporated in the quench process deposits allof the calcitic hydrate in solution (i.e. 1.4 lb./gal.) on the internalpores of the modified coke. The saturated quench solution that finishesthe coke cooling without evaporation will deposit additional calcitichydrate (e.g. 0.8 lb./gal. =1.4-0.6) due to calcitic hydrate's lowersolubility at the elevated temperature (˜100° C). If 80% of thesaturated quench solution is evaporated in coke cooling, roughly 216,800gallons (i.e. 173.4 Mgals. evaporated & 43.4 Mgals heated) of saturatedquench solution would be required each day. If higher quench water ratesare used for process needs (e.g. 200 gal/ton of coke vs. 173.4), thequench solution can be sub-saturated. In addition, the actual solubilityfor each application will need to consider the effects of processcooling requirements, process temperatures, process pressures, and localwater conditions. If necessary, certain chemical agents can be added tothe water to increase the solubility of the calcitic hydrate in water.One skilled in the art can make these adjustments in quench solutionpreparation for each coker application.

[0917] c. Modification of Coker Quench Cycle:

[0918] In the coker quench cycle, the saturated solution of calcitichydrate serves as the quench water and provides the mechanism toimpregnate the porous, modified petroleum coke with calcitic hydrate. Asnoted previously, steam stripping (i.e. “steam out”) may be reduced tokeep more VCM on the coke and allow more water (vs. steam) for coolingthe coke. In fact, the saturated calcitic hydrate solution is expectedto have a significantly lower vapor pressure than the normal quenchwater. This can effectively elevate the vaporization temperature of thequench water: allowing earlier use of quench water (vs. steam) withoutcausing excessive pressure buildup in the coke drums. As notedpreviously, the saturated quench solution is pumped through thesolidifying coke mass in a manner that is very similar to the currentquench cycle.

[0919] As the calcitic hydrate quench solution passes through the hot,solidifying coke mass (temperatures>solution boiling point at processconditions), most of the water in this aqueous quench solutionevaporates and leaves the desired calcitic hydrate integrated in the petcokes crystalline structure. That is, molecular layers of calcitichydrate are deposited on the internal surface of the pet coke,preferably in micropores and mesopores. After the coke has cooledsufficiently (temperatures>solution boiling point at processconditions), evaporation of the quench solution stops. However, thesaturated solution of the calcitic hydrate continues to deposit calcitichydrate on the coke surface due to lower solubilities at elevatedtemperatures. In this manner, much of the calcitic hydrate is uniformlydeposited on coke surface in layers <5 molecules thick (preferably 1molecule thick). That is, the use of a saturated solution providesdeposition at the molecular level (e.g. 0.5 to >10 nanometers). Incontrast, larger crystalline particle sizes (e.g. 1 to 4 microns or 1000to 4000 nm) are associated with suspended calcitic hydrate solids or thetraditional addition of pulverized sorbent in the prior art. Thus, mostof the calcitic hydrate reagent is deposited in the micropores andmesopores as well as the macropores. However, this invention should notbe limited by this theory of operation.

[0920] While cutting the coke from the coke drums, a saturated solutionof the calcitic hydrate should be used for cutting water. This avoidsleaching of the calcitic hydrate from the internal surface of the cokedue to calcitic hydrate solubility in a non-saturated cutting solution.After cutting from the drum, reagent may be exposed to weathering duringshipment and storage. However, rainwater will primarily wash off reagenton exterior surface due to resistance to flow in the micropores andmesopores. Either weather protection or the addition of sufficientcalcitic hydrate is needed to offset this potential problem.

[0921] d. Impacts of Pet Coke Pulverization:

[0922] Pulverization of the modified petroleum coke can exposesignificant amounts of the calcitic hydrate to flame temperatures. Intraditional sorbent injection of the prior art, high temperatureexposure causes sintering of calcitic hydrate, that reduces SOx removaleffectiveness. However, sintering is a phenomenon that primarily affectslarge crystal structures: reactive sorbent is sealed in the crystallinestructure due to blockage of access via sintering. Sintering is notexpected to be a major factor in the current invention due to themolecular nature of the calcitic hydrate. That is, amorphous crystallinechange of the calcitic hydrate, which is one to several molecules thick,does not significantly affect access to unreacted reagent. Thus,sintering is expected to have substantially less impact on the calcitichydrate exposed to flame temperatures as a molecular coating of theexternal coke surface in the current invention. However, this theory ofoperation should not hinder or limit the patentability of this currentinvention.

[0923] e. Performance of Calcitic Hydrate in the Combustion of theModified Pet Coke:

[0924] During the combustion of the modified pet coke, the impregnatedcalcitic hydrate transforms to a more reactive calcitic lime (CaO).Throughout the various stages of combustion, the modified pet coke ofthe current invention effectively (1) protects the lime's reactivesurface area, (2) reduces the traditional kinetic reaction limitationsof dry scrubbing in the prior art, and (3) provides an exemplaryreaction environment with additional reaction mechanisms. As a result,the impregnated calcitic hydrate normally achieves a significantlyhigher reduction of sulfur oxides than dry scrubbing in the prior artfor a given calcium/sulfur ratio.

[0925] In the initial stage of combustion, the modified pet coke of thecurrent invention protects the impregnated calcitic hydrate from highflame temperatures, mitigating sintering effects. In a conventionalpulverized coal burner, the pulverized pet coke, like coal, ispneumatically conveyed via primary combustion air through the coalnozzle of the burner into the hot furnace. In the first 0.01 seconds,the hot furnace temperatures vaporize inherent moisture and devolatilizethe high quality VCMs (e.g. boiling point <750° F.) in the modified petcoke. These gases (i.e. steam and vaporized hydrocarbons), exiting thecoke pores, tend to prevent diffusion of hot gases from the primaryflame into the coke's internal pores. The devolatilized VCMs areoxidized in the first 0.10 seconds, burning in the primary flame zone.As noted previously, the current invention mitigates detrimental effectsof sintering due to (1) protection from exposure to hot flame zones viasurrounding coke char with good insulation properties and/or (2)molecular nature of the calcitic hydrate layer on the internal surfacesof the modified pet coke. The remainder of the petroleum coke is the petcoke char, including its polymeric crystalline structure (e.g. heavyaromatic hydrocarbons and fixed carbon), calcitic hydrate, sulfur, andminimal ash.

[0926] The pet coke char's rate of oxidation is a key factor in theadsorption and chemical conversion of pet coke sulfur. The pet coke charundergoes various reactions over the next 1-2 seconds. As expected, thechar oxidation and higher temperatures predominantly initiate on theexternal surface and work inward. The char oxidation rates primarilydepend on local temperature, oxygen diffusion, particle size, and charreactivity. As the local temperature of the internal coke charincreases, furnace temperatures of combustion products (i.e. flue gas)decrease. The oxidation of pet coke char often occurs at localtemperatures of 950-1600° F. The external surfaces of the pet coke charare closer to flue gas temperatures of 3000-3200° F. just after theprimary flame. In many pulverized coal boilers, this flue gastemperature decreases to 1700-2000° F. at the superheater tubes. At thehigher temperatures, mass transfer of oxygen to the coke char particleis normally the rate-controlling step, in most cases. Thus, oxidation ofthe pet coke char is minimal in the primary flame zone due topredominant oxygen consumption by vaporized VCMs. After this primaryflame zone, char with larger particle size (>30 microns) and/or highmass-to-surface area heat up more slowly and oxidize less quickly. Also,larger char particles tend to lose mass before volume due to theformation and loss of carbon monoxide and carbon dioxide from internalpores. This phenomenon indicates oxygen diffusion into the internalpores prior to total oxidation of the external surface. In addition,activated carbons are capable of catalytic oxidation of organic andinorganic compounds. That is, the oxygen molecules are adsorbed on theactivated carbon surface and broken into very reactive radicals. Thisoxygen activation by the activated carbon is the actual catalytic step.Similarly, the modified coke of the current invention, can adsorb andactivate oxygen molecules. The resulting oxygen radicals will tend toreact with the sulfur ions or compounds within the coke pores at asignificantly lower temperature than traditional sulfur combustion.Consequently, the pet coke char's rate of oxidation can be effectivelycontrolled by the pet coke's particle size distribution. This is usuallycontrolled by the design and operation of the end-user's pulverizationequipment. However, a larger coke particle size distribution canincrease the amount of unburned carbon and decrease combustionefficiency. Therefore, a realistic balance must be achieved between theneed to complete char oxidation before the furnace exit and the desireto maintain a conducive environment for SOx conversion and removal.

[0927] After the primary flame zone, the pet coke char provides areaction environment that promotes the adsorption and conversion of thepet coke fuel sulfur. At temperatures of about 1070° F, the calcitichydrate loses water and transforms to calcitic lime (alias calciumoxide: CaO) with more reactive crystalline structure. This delayedrelease of water and its evaporation are expected to help moderate localtemperatures and further mitigate sintering effects. The freshcrystallization of calcium oxide mostly occurs prior to breakdown ofsulfur compounds and the oxidation of the surrounding coke char. Astemperatures of the coke char exceeds 1100° F., most of the heavyhydrocarbons thermally crack and release sulfur from tight chemicalbonds. The resulting sulfur (or sulfur compound) tends to readilyoxidize significantly before the fixed carbon, heavy hydrocarbons, orcarbon monoxide from the pet coke char. Thus, gaseous sulfur oxides aretypically formed sufficiently prior to the complete oxidation of thechar. As a result, adsorption and conversion of sulfur (e.g. sulfuroxides to calcium sulfate) can preferably take place, while the calciumoxide is still in the protective environment of the pet coke char. Asdiscussed previously, this reaction environment within the internalpores greatly reduces the kinetic reaction limitations of the prior artdue to the close proximity of the reactants and the molecular nature ofthe calcium oxide. That is, diffusion of SOx to the calcium oxideparticle, through its pores, and through any calcium sulfate layers arenormally not reaction rate limiting steps due to their concentratedpresence in the coke pores. Similarly, the prior art's blockage andfilling lime pores by the calcium sulfate is less prohibitive. Inaddition, the thermal cracking and the volatilization of low qualityVCMs (e.g. boiling point >750° F.) are expected to provide greater masstransfer in the internal pores and expose CaO layers on the modifiedcoke's surface.

[0928] All four of the reaction mechanisms (described above) can applyin this exemplary embodiment. Reaction mechanisms 1, 2, and 4 willlikely predominate with the following primary reaction step in each:(Note: reaction can use either sulfur dioxide or sulfur trioxide).

CaO+SO₂+½O₂=CaSO₄; where SO₃ can replace (SO₂+½O₂)

[0929] The desired temperature window for sulfur adsorption and thischemical conversion of sulfur oxides to calcium sulfate is 1600°F.-2300° F. Fortunately, the oxidation of the coke char is expected tooccur in a similar, but slightly higher range of local temperatures. Insome cases, the temperature range may be significantly different,depending on char particle size and the furnace design and operation. Inmost cases, the adsorption and conversion of the sulfur compounds willoccur near the outer boundary of coke char particle. That is, thediffusion of oxygen to the internal pores, as well as local temperatureswill be greater near the exterior surface. Since oxygen diffusion willlikely be limiting, the oxidation of the sulfur compounds, adsorptionand conversion to calcium sulfate can take place before, during, orafter complete oxidation of the adjacent coke structure. Preferably, themajority of the sulfur will be converted to a stable calcium sulfateform prior to local char oxidation. In traditional combustion of highsulfur coal, calcium sulfate is noted to be thermochemically unstable attemperatures >2300° F. This is apparently due to competing reactions inthis reactive, high sulfur environment. However, if most of the pet cokesulfur is converted to calcium sulfate prior to complete coke charoxidation, the high sulfur environment will not likely exist outside thecoke char, where furnace temperatures can exceed 2300° F. Similarly, thedestabilizing environment will not likely exist when the pet coke isused as a blending fuel with low sulfur coals. In the worst casescenario, the calcium sulfate will be released into furnacetemperatures >2300° F. (early stages of coke char oxidation orotherwise). In this worst case, the sulfur in the calcium sulfate willlikely break apart and react with other compounds or remain as SOx. Ifit reacts to form another sulfur salt, it can likely be collected in theparticulate control device. If it remains as SOx, unreacted lime (CaO)from oxidation of coke char near the furnace exit can react attemperatures 1600-2300° F. to form calcium sulfate by the same reactionmechanism as dry scrubbing of the prior art. In either event, removal ofthis sulfur can still occur with downstream particulate control.

[0930] As the char of the modified coke is oxidized and consumed,excess, unreacted lime (CaO) is released from the coke withsubstantially less sintering (vs. lime or limestone mixed with fuel).The excess of unreacted calcitic lime is reflected in the calcium/sulfurratio, adjusted for the SOx removal achieved. As discussed previously,most oxidation of the petroleum coke char occurs at local temperaturesof 950-1600° F. Coke char oxidation is initiated on the external surfacein regions of high flue gas temperatures of ˜3000° F. The coke charoxidation is normally completed in flue gas temperatures down to 1700°F. Thus, unreacted calcitic lime is released into flue gas temperaturesin this whole temperature range (1700-3000° F.). Ideally, most of theunreacted lime is released between 1700° F. and 2600° F. This calciticlime release from the oxidized coke char (analogous to flue gasinjection) can be effective in control of unreacted SOx, either from thepet coke or other sources (e.g. blended coal). This release of unreactedlime can be controlled to some degree by the fuel properties and thecombustion characteristics of the modified coke of the currentinvention. That is, the modified pet coke char would primarily completeburnout in a temperature zone that minimizes sintering, but providesaccess to adsorption of SOx sufficiently prior to the ideal temperaturewindow for optimal reactions. In turn, char burnout and availability ofthe calcitic lime can be controlled, to a certain degree, by the cokeparticle size distribution, VCM quality, and VCM content of the modifiedpet coke. In this manner, the performance of the calcitic lime as thedesired sulfur reagent is significantly improved. Its performance can befurther optimized (to a certain extent) in the combustion of themodified pet coke via process options of the current invention.

[0931] Any unburned pet coke char can be used for adsorption of mercuryand other air toxics in the flue gas downstream of the furnace. If petcoke char remains unoxidized, some sulfur ions in the internal pores arelikely to be unoxidized, as well. These sulfur ions can react withmercury, which is adsorbed on the pet coke surface, to form mercurysulfide (HgS). Sulfur impregnated activated carbons, used for mercuryremoval, have similar types of chemisorption reaction mechanisms. Inaddition, remaining pet coke char can also have sufficient porosity andsurface area to adsorb dioxins and other air toxics in the flue gas fromthe pet coke or other sources.

[0932] (4) Other Embodiments

[0933] a. Supersaturated Solutions of Calcitic Hydrate:

[0934] Another embodiment of the current invention is the use of asupersaturated solution of calcitic hydrate for coke quench water. Thisembodiment is desirable in cases where a saturated solution of calcitichydrate is not sufficient to achieve the Ca/S ratios required for highercoke sulfur levels and/or higher sulfur removal requirements of aparticular application.

[0935] Various means can be used to achieve a supersaturated quenchsolution of calcitic hydrate in water. The simplest means would includethe use of chilled water to increase solubility of the calcitic hydrate(Ca(OH)₂) in water. Unlike most solutes, calcitic hydrate or calciumhydroxide has decreasing solubility characteristics as temperatureincreases. Thus, chilling the quench water increases the solubility and,hence, the quantity of calcitic hydrate totally dissolved in solution.As the temperature increases, the calcitic hydrate would remain insolution as long as there are no suspended particles that nucleate andprecipitate the calcitic hydrate out of solution. Also, suspendedcalcitic hydrate cannot be available to remain in equilibrium with thesolution. This supersaturated solution could then be used as coke quenchin the coker quench cycle. As such, incremental amounts of calcitichydrate would be deposited in the internal crystalline structure of themodified pet coke. The lower temperature limit (or upper solubilitylimit) for this approach is less than the freezing point of the puresolvent (i.e. water@32° F.) due to the freezing point depression of thesolvent in solution.

[0936] Unfortunately, this supersaturated solution can be difficult toachieve on a consistent basis in a coker process environment. Impuritiesin the recycled coke quench water (e.g. other calcium compounds orsuspended coke fines) can serve as nucleation to precipitate excesscalcitic hydrate out of solution before reaching the coke drums as cokequench. In addition, the preparation of the supersaturated solution maynot be practical, in many cases, due to other technical and economicconsiderations. Furthermore, the increase in solubility of thesupersaturated solution may still not be sufficient to provide thedesired calcitic hydrate, totally dissolved in the coke quench solution.

[0937] b. Saturated Solution of Calcitic Hydrate with Suspended CalciticHydrate Solids:

[0938] An alternative embodiment to the saturated or supersaturatedsolution (calcitic hydrate in water) would be the use of a saturatedsolution with suspended solids of calcitic hydrate. Again, thisembodiment is desirable in cases where a saturated or supersaturatedsolution of calcitic hydrate is not sufficient to achieve the Ca/Sratios required for higher coke sulfur levels and/or sulfur removalrequirements of a particular application. In this embodiment, thecalcitic hydrate would be preferably produced without the traditionalagglomeration step and/or pulverized to the smallest practical particlesize distribution: <4 microns and preferably 100%<1 micron. In manycases, most of the calcitic hydrate will still be deposited out of thesaturated solution onto the internal surfaces of the modified coke'smicropores and mesopores. The residual lime from solution and thesuspended lime solids will be deposited on the macropores. That is, muchof the suspended calcitic hydrate solids (1-4 micrometers) will not besmall enough to be integrated into the micropores (diameter <2nanometers) and mesopores (d=2-50 nanometers), but deposited in themacropores (d>50 nanometers). As noted earlier, cutting the coke fromthe drums and pulverization to a fineness of 70-95% <200 mesh (d=˜74micrometers) can cause significant portions of the calcitic hydratedeposited on the macropore walls to become part of the external surfaceof the coke particles. This potentially exposes these reagents toweathering during transport and high-temperature flame zones in thecombustion process, respectively. The calcitic hydrate suspended solidsdeposited in the coke macropores are more likely to suffer detrimentalsintering effects (vs. dissolved calcitic hydrate deposited fromsolution). This is primarily due to their larger particle size (vs.molecular layers <2 nanometers). In contrast, the rest of the calcitichydrates deposited on the macropore walls will still be part of theinternal surface of the coke particles after pulverization. Theproportion of each will depend on the coke crystalline structure and thetype/degree of coke cutting and pulverization. In any case, the Ca/Sratio will likely need to be increased to compensate for losses toweathering and sintering of some suspended solids of calcitic hydrate.In many cases, this will partially offset the improvements in reagentutilization for the desired SOx removal efficiency. One skilled in theart can readily make adjustments in Ca/S ratios to achieve the desiredSOx removal efficiency for a particular application of this technology.

[0939] c. Various Solutions of Dolomitic Hydrates as Coke Quench:

[0940] As noted above, dolomitic limes can be preferable sulfur reagents(e.g. sorbents) to calcitic limes in some cases. In certainapplications, the impregnation with dolomitic hydrates (Ca(OH)₂ with MgOor Mg(OH)₂) is preferable to calcitic hydrate due to (1) greaterresistance to sintering, and/or (2) higher sulfur reactivity. Either orboth of these reasons can lead to higher sulfur removal capabilities. Inthese cases, proper consideration should be given to additional costs,higher ash loading in boiler/particulate control device(s), andmagnesium impacts on ash fouling/reuse characteristics. In manyapplications, however, the higher SOx removal efficiencies can be morecritical than these concerns. The impregnation of the modified pet cokewith dolomitic hydrates may normally be similar to the exemplaryembodiment (described above). Various solutions of dolomitic hydratescan be used as coke quench in the delayed coker quench cycle: saturated,sub-saturated, and saturated with suspended dolomitic hydrate solids.

[0941] The dolomitic hydrates have two primary forms: monohydrate anddihydrate. Both forms are made form dolomitic quicklime, which isderived from limestone containing 35 to 46 percent magnesium carbonate.The monohydrate (or atmospheric hydrated dolomite) has the hydrate ofquick lime (CaO) with magnesium oxide: Ca(OH)_(2*)MgO. The monohydratetypically has the following chemical composition: 46-48 wt. % calciumoxide, 33-34 wt. % magnesium oxide and 15-17 wt. % chemically combinedwater. The dihydrate (or pressure hydrated dolomite) has the hydratedoxides of both calcium and magnesium: Ca(OH)_(2*)Mg(OH)₂. The dihydratetypically has the following composition: 40-42 wt. % calcium oxide,29-30 wt. % magnesium oxide and 25-27 wt. % chemically combined water.The dihydrated form of dolomitic lime (i.e.Ca(OH)_(2*)Mg(OH)₂) isnormally preferable over the monohydrate form due to generally higherspecific surface area and smaller particle size distribution inconventional production. Both of these factors provide incremental SOxremoval.

[0942] This embodiment using dolomitic hydrates can best be summarizedby again reviewing (1) selection of dolomitic hydrates as desired sulfurreagent, (2) preparation of the coke quench solutions, (3) modificationof quench cycle in the coking operation, (4) pulverization of pet cokefuel, and (5) performance of the reagent in the combustion of themodified pet coke.

[0943] c1. Selection of Dolomitic Hydrates as Sulfur Reagent:

[0944] The primary differences between dolomitic hydrates and calcitichydrates are resistance to sintering, reactivity, and solubilitycharacteristics. First, sintering studies with furnace injection of theprior art have shown that calcitic hydrates can lose up to 50% of itsBET surface area in furnace temperatures >2000° F. In contrast,dolomitic hydrates can increase up to 50% in surface area in similarprior art conditions. As such, dolomitic hydrates apparently have a muchgreater resistance to sintering. Secondly, the sulfur reactivity of thedolomitic hydrates is enhanced by the presence of the magnesium. Thoughit improves calcium utilization, magnesium is essentially chemicallyinert in the prior art furnace injection. Also, the unreacted magnesiumcan detrimentally impact ash fouling characteristics, total ash loading,and ash reuse/disposal. In the prior art, studies have shown that SOxremoval on a mass basis (i.e. Lbs. SOx/Lbs. Sorbent) is similar forcalcitic hydrate and dolomitic hydrates. However, prior art studies havealso shown that dolomitic hydrates are capable of up to 75% SOx removalvs. up to 60% for calcitic hydrate. In addition, the dolomitic hydratesin the current invention will have additional reaction mechanisms toreact with non-oxide forms of sulfur (discussed below). Finally, thesolubility of dolomitic hydrates is slightly higher due to the weakerbonds of a less symmetrical crystalline structure (i.e. dolomitichydrates as a solute). Unfortunately, the degree of unreacted magnesiumcan offset the ability to totally dissolve a greater mass of dolomitichydrates.

[0945] c2. Preparation of Coke Quench Solutions With Dolomitic Hydrates:

[0946] Overall, dolomitic hydrates have very similar physical andchemical properties as calcitic hydrate. As such, the above discussionsregarding calcitic hydrate and its associated quench solutions generallyapply to dolomitic hydrates, as well. The various coke quench solutionsof dolomitic hydrates are discussed below, primarily noting anysignificant differences:

[0947] 1. Saturated and Sub-Saturated Solutions of Either DolomiticHydrate: The solubility of dolomitic hydrates are generally higher thancalcitic hydrate due to their weaker crystalline structures with thepresence of both magnesium and calcium (i.e. vs. pure Ca(OH)₂ or pureMg(OH)₂). This typically allows coke impregnation of greater mass forthe dolomitic hydrates. In many cases, the increased reactivity of themagnesium in the current invention makes the higher solubilityadvantageous. In contrast, the unreactive nature of the magnesium withfurnace injection of the prior art often negates this advantage. Inaddition, the decrease in water solubility associated with increasingtemperature can be substantially lower in dolomitic hydrates (discussedin item 2.). Thus, less mass of dolomitic hydrates can be impregnated inthe coke without evaporation of coke quench, in many cases.

[0948] 2. Supersaturated Solution of Either Dolomitic Hydrate:Supersaturated solutions of dolomitic hydrates are more difficult toachieve than supersaturated solutions of calcitic hydrate. As discussedpreviously, calcium oxide (CaO) and calcium hydroxide (Ca(OH)₂) have anunusual solubility characteristic: lower water solubility withincreasing temperature. In contrast, magnesium oxide (MgO) and magnesiumhydroxide (Mg(OH)₂) increase in water solubility with increasingtemperature. Though some dolomitic hydrates contain equal moles ofcalcium and magnesium compounds, the degree of solubility increase forchilled water will be significantly less, and partially depend on thetype and origin of the dolomitic hydrates. Thus, other means of creatinga supersaturated solution would be required in many cases.

[0949] 3. Saturated Dolomitic Hydrate Solution with Suspended DolomiticHydrate Solids: This approach is very similar to a saturated solutioncontaining suspended calcitic hydrate solids. Conventional production ofthe dihydrate form has particle size of roughly 1.0-4.0 micrometers,which is similar to calcitic hydrate. However, conventional productionof the monohydrate form typically has particle size of 14-20micrometers. With either dolomitic hydrate, the size of the suspendedparticles should be as small as practical (preferably <1.0 micron) forthe particular application.

[0950] c3. Modification of Coke Quench Cycle in the Coking Operation:

[0951] The coke quench cycle is very similar to the description forcalcitic hydrate. The primary difference is modifications to compensatefor differences in solubility characteristics: water solubility atambient temperatures and related temperature effects. One skilled in theart can make modifications in equipment and operations to address theseconcerns in particular applications of the current invention.

[0952] c4. Impacts of Pet Coke Fuel Pulverization:

[0953] The pulverization impacts for pet coke with dolomitic hydratesare very similar to the pulverization description for the exemplaryembodiment. The primary difference is dolomitic hydrates have greaterresistance to sintering. Thus, the dolomitic hydrates left on theexternal surface of the fuel coke particles due to pulverization willmaintain higher sulfur removal capabilities. Again, the dolomitichydrates, that are deposited from dissolved solution (not suspendedsolids), have molecular layers that are less prone to sintering, even onthe external surface of the pulverized coke particles. Though the cokechar of the current invention offers protection from sintering, thisresistance to sintering can be advantageous, particularly on theexternal surface of the pulverized coke particles. One skilled in theart can make modifications in equipment and operations to optimize theseconcerns in particular applications of the current invention.

[0954] c5. Performance of Dolomitic Hydrates in the Combustion of theModified Pet Coke:

[0955] The most important difference in the use of dolomitic hydratesversus calcitic hydrate is its potential for higher sulfur removalcapabilities. The improved performance of dolomitic hydrates in thecurrent invention is due to two primary factors: (1) magnesium and petcoke's roles in reducing detrimental sintering effects and (2) enhancedsulfur reactivity of magnesium.

[0956] Reduced sintering effects in the current invention can improvethe sulfur removal performance of the dolomitic hydrates over their usein the prior art. As discussed earlier, the magnesium of the dolomitichydrates substantially increases the calcium utilization in the priorart, primarily due to the much greater resistance to sintering. That is,furnace injection of the dolomitic hydrates has shown an increase insurface area up to 50% (vs. up to 50% reduction in BET surface area forcalcitic hydrate). In the current invention, this phenomenon is expectedto increase the surface area. Hence, SOx removal is higher for anydolomitic hydrates deposited from suspended solids. This can beparticularly true for dolomitic hydrates on pores that become part ofthe external surface of the coke particles after pulverization. Inaddition, the molecular deposition from dissolved dolomitic hydrates isexpected to also reduce impacts of sintering, as noted before. That is,the insulation properties of the modified pet coke offer sinteringprotection for dolomitic hydrates deposited in the internal pores.Consequently, the overall impact of the current invention is to furtherreduce the detrimental effects of sintering and further enhance thecalcium utilization, in most cases.

[0957] The sulfur reactivity of magnesium can be substantially enhancedby the current invention in two ways: (1) improvement of magnesiumreactivity with sulfur oxides and (2)promotion of magnesium reactivitywith non-oxide forms of sulfur. First, the reaction of magnesium withsulfur oxides (SOx) in the prior art is apparently very limited due tothe unstable nature of magnesium sulfate at the furnace injectiontemperatures (e.g. MgSO₄ decomposes at temperatures >2050° F.). Themodified petroleum coke of the current invention can effectivelyinsulate, to a certain extent, this desirable reaction from hightemperature zones (i.e. >2000° F.). As the coke char increases intemperature to roughly >660° F., any magnesium hydroxide (i.e. hydratedmagnesium oxide Mg(OH)₂) in the dolomitic dihydrate losses water;dehydrating to form magnesium oxide (MgO) crystals. As the coke charreaches temperatures >1000° F, the heavy organic compounds (i.e.aromatics, asphaltenes, & resins) in the polymeric coke structure startto thermally crack or break apart at a molecular level. These crackingreactions release carbonium ions and sulfur (or sulfur complex) ions inthe vapor state. If oxygen is available at the coke surface, the sulfurions readily oxidize to form sulfur oxides. The gaseous sulfur oxidescan then migrate along the coke surface until converted by the calciumoxide and/or magnesium oxide. The modified pet coke can shield thesereactants in its internal pores for sufficient time to form MgSO₄ andprevent exposure to temperatures above 2000° F. Unfortunately, highconcentrations of oxygen are not generally available in the coke's innerpores at lower temperatures. Secondly, a high degree of unoxidized cokechar downstream of 2000° F. flue gas temperatures is not desirable, inmost cases, due to low combustion efficiency and other considerations.Therefore, magnesium reactivity with sulfur oxides is often improved(vs. prior art) by this reaction mechanism of the current invention, butonly to a limited extent.

[0958] An alternative reaction mechanism of the current inventionpromotes magnesium reactivity with non-oxide forms of sulfur. Again, theheavy organic compounds (i.e. aromatics, asphaltenes, & resins) in thepolymeric coke structure start to thermally crack at temperatures over1000° F, and release carbonium ions and sulfur (or sulfur complex) ionsin the vapor state. These very reactive carbonium and sulfur ionstypically oxidize when oxygen is present. However, the internal poresand even some of the external surface of the coke char are not readilyexposed to oxygen at the early stages of the char oxidation. Thesegaseous ions can migrate within the coke pore structure to the reactionsites of magnesium oxide. In the proper conditions at these hightemperatures, the very reactive carbonium and sulfur ions can exchangeionic bonds oxidizing the carbonium ion and forming magnesium sulfide(MgS). Unlike calcium sulfide (CaS), magnesium sulfide isthermochemically stable at these temperatures and higher (i.e.decomposes at T>3632° F.). It is also a collectible particulate at theseand lower temperatures. Chemisorption occurs, if the impregnatedmagnesium oxide reacts with the sulfur compounds adsorbed on the carbonsurface (i.e. reaction mechanism 2. in the general discussion of thecurrent invention). This reaction mechanism is analogous to gaseousmercury (Hg) reacting with solid sulfur crystals impregnated onactivated carbon at much lower temperatures. In this manner, part of themagnesium, which is essentially chemically inert in the prior art,becomes reactive in the current invention. The degree of sulfurreactivity depends on various factors, including the (1) localtemperature, (2) types, reactivity, and diffusion of the carbonium &sulfur ions, and (3) length of time carbon char internal pores orsurface remains without oxygen. These factors are influenced by the petcoke's composition, crystalline structure, and degree of pulverization.The design and operation of the furnace in the pet coke user's systemalso influence them. This reaction mechanism is not the only means bywhich magnesium's sulfur reactivity is increased in the currentinvention. As such, the present invention should not be limited by thistheory of operability.

[0959] Another major benefit of using dolomitic hydrates is asubstantial reduction of the detrimental effects of heavy metals (e.g. V& Ni) in the petroleum coke. The dolomitic hydrates mitigate superheaterfouling, high temperature ash corrosion, and low temperature sulfuricacid corrosion. Dolomite is currently used as a combustion additive inheavy fuel oil firing to alleviate these problems. The reduction offouling and high temperature corrosion is basically achieved byproducing high melting point ash deposits, that can easily be removed bysootblowers or lances. Low temperature sulfuric acid corrosion isreduced by the formation of refractory sulfates by reaction with thesulfur trioxide (S0₃) gas in the flue gas stream. By removing the sulfurtrioxide, the dew point of the flue gas is sufficiently reduced toprotect the metal surfaces. Similar to the dolomitic hydrates, thedolomitic carbonates (i.e. dolomite) calcine into the oxides ofmagnesium and calcium, after heating in the primary flame zone (i.e.losing carbon dioxide vs. water). The sulfating ability of these oxidesproduces dry, collectible ash compounds (e.g. CaSO₄ & MgSO₄), and limitundesirable compounds of vanadium, nickel, and sulfur (e.g. vanadiumpentoxide, sulfates of Ni, Na, & K; & various vanadates). In prior artpractices, the magnesium oxides, as well as the calcium oxides, reactwith sulfur oxides to form sulfates. This occurs despite being injectedwith the fuel oil and exposed to the primary flame without protectionfrom sintering effects. The amount of fuel additive is generally equalto the ash content of the fuel or 2-3 times the vanadium content. Thelafter is normally prescribed in situations, where high temperaturecorrosion is the primary concern. However, the amount of dolomitichydrates impregnated on the petroleum coke in the current invention isnormally in substantial excess of either amount. Therefore, theimpregnated dolomitic hydrates should readily mitigate the detrimentaleffects of the heavy metals in the petroleum coke.

[0960] In conclusion, dolomitic hydrates can be the desired sulfurreagent in many applications of the current invention. The primarybenefits of dolomitic hydrates include (1)increased sulfur reactivity,(2) increased solubility in water, (3) less sintering effects, and(4)proven ability to mitigate ash problems with heavy metals in fuel.These benefits are particularly advantageous in cases where magnesium issignificantly more reactive than dolomitic sorbent injection of theprior art. The primary detriments of dolomitic hydrates includeadditional costs and potential negative effects of magnesium on ashquality and quantity. These factors need to be properly evaluated foreach application of the current invention. One skilled in the art canmake such evaluations and determine the most desired sulfur reagent.Appropriate process options of the current invention can be employed,based on performance requirements, engineering calculations, and tests,if necessary.

[0961] d. Mixture of Calcitic Hydrate and Dolomitic Hydrates:

[0962] The sulfur reagent impregnated on the modified pet coke of thecurrent invention can be optimized by various mixtures of calcitichydrate and dolomitic hydrates. This alternative embodiment potentiallyoffers the opportunity to optimize the physical & chemical propertiesand achieve the optimal sulfur reagent. In this manner the potentialbenefits can be maximized and/or the risks/detriments minimized. Thepreparation and use of such mixture would be very similar to the abovediscussions for the exemplary embodiment and the alternative embodimentfor dolomitic hydrates.

[0963] e. Other Types of Reagents:

[0964] Other types of sulfur reagents can be impregnated on the internalsurface of the modified pet coke using the same methodology of thecurrent invention. These sulfur reagents can react with various forms ofsulfur (i.e. with and/or without sulfur oxides). Other sulfur reagentswould include, but should not be limited to the following:

[0965] 1. Other Alkaline Earth Metal Reagents: Limestone, dolomite,limes, magnesia, etc.

[0966] 2. Alkali Metal Reagents: Potassium hydroxide, sodium hydroxide,potassium iodide, etc.

[0967] 3. Other Sulfur Reagents: Transition element compounds, Nonmetalcompounds, etc.

[0968] As noted previously, alkali metal reagents, particularly sodiumreagents, have a tendency to form undesirable compounds (e.g. varioussodium vanadates) before reaching the desired temperature window in thecombustion system to react with sulfur oxides. However, the increasedsolubility may be very advantageous in cases where pet coke heavy metalsare not a major problem. Also, sulfur reagents with certain solubilitycharacteristics (e.g. like calcium hydroxide) can be used in quenchwater even without the evaporation of the water.

[0969] For each type of sulfur reagent, the stoichiometric ratios andreaction temperature windows in the combustion environment would need tobe determined for the desired or optimal sulfur removal efficiencies.One skilled in the art can use this information to modify themethodology of the current invention to achieve the desired impregnationof the petroleum coke.

[0970] f. Combination of Sulfur Reagents:

[0971] A combination of any of the above sulfur reagents, includingcalcitic and dolomitic hydrates, can be used to optimize physical andchemical properties for coke impregnation and sulfur conversion. Forexample, a combination of sulfur reagents could be used to overcomesolubility limits that prevent the impregnation of sufficient amounts ofa sulfur reagent in a reasonable quantity of quench water. For example,the combination of calcium hydroxides and potassium hydroxides couldprovide several advantages.

[0972] g. Combination of Impregnated Sulfur Reagent with Other Types ofSulfur Removal:

[0973] In some applications of the current invention, the combination ofimpregnated sulfur reagent on the pet coke and other sulfur removaltechnologies may be desirable to optimize/maximize sulfur removal. Thatis, the combined sulfur removal technologies can provide additional ormore optimal sulfur removal. Furthermore, other sorbent injectionsystems can enhance SOx removal sufficiently in cases where sufficientSOx removal is not possible due to high coke sulfur levels and/or ashloading limitations (i.e. beyond reach of soluble sorbents and sinteredsuspended solids). For example, calcitic hydrate in economizer at fluegas temperatures near 840 to 1020° F. can effectively supplement thesulfur removal from pet coke impregnated with sulfur reagent(s). In somecases, lime is already used on-site for other purposes (e.g. watertreatment). Incremental costs of additional lime capacity and injectiongrid can be minimal due to reduced size of the required system. Thissolution, however, may limit boiler load fluctuations due to temperaturesensitivity of injection zone for various boiler loads. Also, minimumimpregnation of pet coke with dolomitic hydrates may be desirable tomitigate ash and corrosion problems associated with heavy metals infuel. In this manner, a separate sorbent injection system can provideany additional SOx removal required.

[0974] h. Additives to Enhance Solubility Characteristics and/orResistance to Sintering:

[0975] Certain additives can be used to enhance solubilitycharacteristics and/or resistance to sintering. Both thesecharacteristics of the sulfur reagent(s) depend on the strength of thecrystalline structure. For solubility, a weaker crystalline structurecauses higher solubility in water. For resistance to sintering, astronger crystalline structure at higher temperatures preventssintering, which is essentially the partial collapse of the crystallinestructure. Ideally, the crystalline structure of the sulfur reagent inthe current invention is stronger as the temperature increases. That is,weaker crystals in cold water allow high solubility in coke quenchwater. At higher temperatures, the stronger crystalline structuredecreases water solubility, which allows deposition of sulfur reagenteven without quench water evaporation. The stronger crystallinestructure at high temperatures also improves resistance to sinteringsignificantly. Unlike most salts, calcitic hydrates have this physicalproperty: lower water solubility at higher temperatures and someresistance to sintering. The magnesium in dolomitic hydrate apparentlystrengthens the crystalline structure(s) at higher temperatures. As aresult, the water solubility at ambient temperatures is increased, thewater solubility >200° F. is slightly lower, and the resistance tosintering is substantially improved. It should be noted that thedolomitic hydrate has a greater capacity for deposition from quenchwater that is either evaporated or not evaporated. In a similar manner,other additives can be used to enhance the solubility characteristicsand resistance to sintering in other sulfur reagents of the currentinvention.

[0976] i. Soaking or Spraying Impregnation of Sulfur Reagent on the PetCoke:

[0977] Methods of impregnation similar to activated carbon impregnationcan also be used for the modified pet coke of the current invention. Thebasic methods soaking and/or spraying methods can be used to impregnatesulfur reagent on the modified pet coke. Unfortunately, the impregnationwill likely predominate near the exterior surface, due to lack ofpenetration into the internal pores. Consequently, the sinteringprotection offered by the pet coke char would be limited in many cases.

[0978] j. Impregnated Pet Coke in Staged Fuel Burners:

[0979] The modified pet coke impregnated with sulfur reagent can beeffectively used in staged burners that moderate temperature profilesand make sintering less detrimental. As discussed previously, low NOxcombustion technologies tend to create less intense combustion thatlengthens the primary flame zones and moderates flame temperatures. Thistends to reduce sintering of the sulfur reagent. In addition, some lowNOx combustion techniques employ staged fuel combustion to “reburn” theprimary flame combustion products in a reducing atmosphere that reducesNOx. If solid fuels are used in the second stage (current burners tothose yet to be designed), a modified pet coke of the current inventioncan be optimized for this service. Since the secondary fuel is notexposed to the high temperatures of the primary flame zone, theimpregnated sulfur reagent would experience less sintering and requireless sintering protection from the pet coke char. Consequently, themodified pet coke can be optimized via process options of the currentinvention to provide the reducing atmosphere to decrease NOx, completecombustion in the firebox, and still offer desired SOx removal.Examples: US DOE/B&W's Limestone Injection Multistage Burner (LIMB) orReburn burners for Low NOx combustion, particularly in cyclone boilers.

[0980] k. Impregnated Pet Coke with High-Calcium Coals:

[0981] Some coals (e.g. subbituminous) have high calcium concentrationsdue to inherent limestone deposits within the coal seams. If themodified pet coke of the current invention is blended with such coals,the calcium in these coals can react with the sulfur oxides to formcollectible sulfates. However, as noted earlier, exposure of thiscalcium (e.g. CaO) to the primary flame can substantially reduce itseffectiveness as a sulfur reagent due to sintering effects. If thecalcium present in the coals is due to dolomite deposits within the coalseams, the sintering effects are probably reduced substantially. Ineither case, the calcium in the fuel blended with the pet coke canreduce the sulfur oxides to some degree. Thus, modifications to theimpregnation (e.g. reduction in Ca/S stoichiometric ratio) andcombustion characteristics (e.g. VCM quantity & quality) of the modifiedpet coke should reflect this effect on SOx removal. Depending on theblending proportions, this could eliminate the need for impregnation ofsulfur reagent altogether in some cases.

[0982] B. Adsorption & Other Impregnation of Pet Coke Pores:

[0983] Enhanced Fuel Qualities

[0984] The ability to use the carbon adsorption character of themodified coke to improve fuel properties was briefly described earlierin the current invention. Various hydrocarbons and other non-polarcompounds are added to the modified coke via adsorption. Similar to thesulfur reagents, other chemical agents are added via impregnation. Bothadsorption and impregnation are accomplished via the coke quench of thedecoking cycle. The adsorption and impregnation of desirable compoundsare discussed below in further detail.

[0985] (1) Addition of Volatile Combustible Materials (VCMs):

[0986] As described previously, the addition of volatile combustiblematerials (VCMs) to the modified pet coke can be advantageous in manyapplications of the current invention. Both the quality and quantity ofVCMs are key factors in improving fuel character and performance.

[0987] The volatile matter or volatile content of a fuel is determinedby ASTM Method D 3175. In this test method, all vaporized compounds whena fuel reaches 950+/−20° C. (1742+/−68° F.) for seven minutes areconsidered volatile content. These compounds normally include moisture,carbon monoxide, and various hydrocarbons. As such, the volatile contentis composed of organic and inorganic compounds. On the other hand,Volatile Combustible Materials (VCMs) refers to these compounds that canbe oxidized further in a combustion environment. Though VCMs can beinorganic (e.g. carbon monoxide), most VCMs are organic, hydrocarboncompounds with various degrees of hydrogen saturation.

[0988] For the current invention, Volatile Combustible Materials (VCMs)are classified by boiling points: high-quality: <750° F, medium quality:750 to 950° F, and low-quality: >950° F. The high quality VCMs primarilyhelp with initiating and sustaining combustion. The low quality VCMsprimarily help with char burnout. The medium quality VCMs can help witheither depending on the point of release in the combustion process andthe degree of difficulty in oxidation. Consequently, VCM performance inthe modified coke of the current invention depends on types of VCMcompounds, costs, and physical & chemical properties. Cost vs.performance trade-offs need to be evaluated for each application.Ideally, waste streams of acceptable quality (e.g. used lubricating oilsand certain hazardous wastes) are readily available.

[0989] The integration of VCMs on the pet coke in the current inventionoccurs in two key stages. First, VCMs (mostly low-quality) increase dueto the coker process modifications that assure sponge coke and increaseporosity. The quantity of this increased VCM depends on the severity ofthe process changes (described earlier). The VCM quality depends on thetypes of VCM compounds that become part of the modified pet cokecrystalline structure. Secondly, VCMs can be added to the modified petcoke via the coke quench. The addition of VCMs normally involves (butnot always) the improved carbon adsorption characteristics of themodified coke. Most, if not all, of the VCMs integrated on the modifiedpet coke are organic hydrocarbons that are fairly insoluble in water.After the pet coke has cooled sufficiently to prevent vaporization ofthe VCMs, the chosen VCMs can be injected into the coke quench water.The improved carbon adsorption properties of the modified coke causeeffective adsorption of most VCMs on the internal surface area of thepet coke pores. As discussed earlier, the relative sizes of the VCMmolecules and the modified coke's pores will determine adsorptioneffectiveness. In this manner, the quantity and quality of the VCMs canbe controlled. Desirable VCMs that are somewhat soluble in water (e.g.alcohols, phenols) can still be integrated into the modified pet cokevia a combination of carbon adsorption and solubility characteristics.For example, a fairly non-polar alcohol can be adsorbed, particularly ifthe quantity of alcohol is greater than saturation. However, polar VCMsthat are very soluble in water can be more difficult to adsorb. If theseVCMs have high boiling points, impregnation similar to sulfur reagentsmay be possible. Consequently, evaluation of the adsorption of low-costVCMs can be required. One skilled in the art can readily evaluateavailability, costs, and the properties of VCMs to determine the optimalVCMs to integrate on the pet coke for specific applications of thecurrent invention.

[0990] (2) Addition of Ionizing Compounds:

[0991] The addition of ionizing compounds to the modified petroleum cokecan be advantageous in certain combustion applications. Ionizingcompounds can be selected from various chemical agents that increasesthe quantity and/or quality of ions in the high-temperature, combustionproducts (e.g. plasma). Alkali metals typically have the lowestionization energies. Alkaline earth metals are the family of elements ofnext lowest ionization energies. As such, ionic compounds (e.g. oxides,hydroxides, carbonates, etc.) of alkali metals and akaline earth metalshave many desirable characteristics of ionizing agents. Many of theseionizing compounds are the same compounds that are desirable for SOxsorbents. Likewise, the addition of these ionizing agents to fuel-gradepetroleum coke has similar concerns to the addition of sulfur sorbents.That is, their undesirable ash compounds and solubility issues make thealkali metal compounds less desirable than the alkaline earth compoundsin many cases. Consequently, the addition of calcitic hydrate is anexemplary embodiment for the addition of ionizing compounds, as well.The preference for this ionizing agent can be dependent on thecombustion application and other pet coke properties. In addition, otherembodiments for the addition of ionizing agents would include, butshould not be limited to (1) other calcitic, dolomitic, potassium,and/or sodium compounds, (2) addition via coke quench solution(saturated, sub-saturated, supersaturated, and saturated with suspendedsolids), and/or (3) in combination with other chemical additives thatenhance ionization.

[0992] As discussed previously, Magnetohydrodynamic (MHD) electricgeneration is a prime example of advantageous addition of ionizingagents to modified pet coke. MHD occurs when hot, partially ionizedcombustion gases (plasma) are expanded through a magnetic field. The hotgas can be produced in a ceramic coal combustor with temperaturesapproaching 5000° F. Even at these high gas temperatures, the availablegas ionization normally needs to be increased significantly. Thus, MHDtechnology often requires the seeding of the hot plasma gas withionizing compounds. Various types of ionizing compounds can be used,including calcitic hydrate. However, potassium hydroxide can bepreferable due to ease of ionization, if potassium hydroxide solubilityand resulting ash compounds are not prohibitive. In these cases, oneskilled in the art can determine the proper quantity of potassiumhydroxide desired and make adjustments to the type of coke quenchsolution (e.g. saturated).

[0993] Coal has been traditionally used as the preferred fuel in theresearch for MHD technology. The modified pet coke of the currentinvention offers many advantages over various coals for MHD technology.First, the modified pet coke has >90% less ash, >25-60% greater heatingvalue, and substantially lower moisture content. These characteristicspotentially provide higher flame temperatures, lower air/oxygentemperature requirements, and/or less ash problems in combustor anddownstream heat exchange. Secondly, the pet coke can be readilypulverized to a finer particle size distribution to assure compact,intense, and efficient flame generation. Finally, VCMs, ionizing agents,and/or other desirable compounds (e.g. oxygen-containing) can beuniformly added to the modified coke of the current invention. That is,coke quench would provide the means to add ionizing agents in a mannersimilar to sulfur reagents. The quality and quantity of thesepotentially desirable compounds can be optimized, as well.

[0994] An exemplary embodiment of the current invention for MHDtechnology may include modified pet coke production from a sweet crudecoker. Thus, the modified pet coke would have low-sulfur and low-metalscontents to prevent downstream ash problems. Also, the modified pet cokewould have a high porosity, crystalline structure that would allow veryfine pulverization (>90% through 200 mesh). The quantity and quality ofVCMs (via modified coker process conditions and/or coke quench addition)can be optimized to initiate and sustain combustion. The finepulverization and optimal VCMs provide efficient combustion with astable, compact flame. In addition, oxygen-containing compounds can beadded to reduce the required air/oxygen stream, if desirable. Finally,potassium hydroxide or potassium iodide can be readily added as theionizing agent via coke quench. That is, the solubility of eitherpotassium compound is sufficient to uniformly deposit molecular layersvia a saturated quench solution during the entire quench cycle. That is,the evaporated quench solution will leave the molecular layers on theinternal pores of the modified pet coke. The non-evaporated quench wouldstill be saturated to prevent uptake of the deposited potassium compoundinto an unsaturated quench solution. One skilled in the art candetermine the proper quantity desired for the MHD application, andimpregnate them on the pet coke via coke quench. The use of saturated,sub-saturated, super-saturated, or saturated with suspended solids isagain similar to the exemplary embodiment for the addition of SOxsorbents.

[0995] (3) Addition of Oxygen-Containing Compounds:

[0996] Various types of oxygen compounds can be added to the modifiedpet coke to reduce excess air required and/or reduce impact of oxygendiffusion as a kinetic reaction limitation for various reactions (e.g.sulfur reagents). For either purpose, the oxygen compound, in general,will make the oxygen readily available to react with other species athigher temperatures. In other words, the oxygen compound will generallybe an oxidizing agent. The type of oxygen compound can determine itsrole. For example, oxygen compounds that have boiling points <750° F.will likely volatilize in the primary flame zone. This can reduce excessair requirements for the primary flame zone and improve low NOxcombustion. Secondly, an oxygen compound that has a boiling point >950°F. (e.g. large, phenolic compounds) can help char oxidation and reduceoverall excess air requirements for complete combustion. Also, this typeof oxygen compound can provide oxygen in the internal pores to promoteearlier oxidation of sulfur. In turn, this can help promote desired SOxreaction mechanisms reaction with sulfur reagent(s).

[0997] As with VCMs, the addition of oxygen compounds can beaccomplished with wither coke adsorption or impregnation via solubilitycharacteristics. In either case, the oxygen compounds are integrated viathe coke quench solution. Selection of the optimal oxygen compounddepends on desired performance, availability, costs, andphysical/chemical properties. One skilled in the art can determineoptimal oxygen compound(s) to integrate on the pet coke for specificapplications of the current invention.

[0998] (4) Optimization of Coke Fuel Catalyst Properties:

[0999] The ability to optimize the oxidation catalytic activity in themodified pet coke has been previously discussed. Combustion of themodified pet coke of the current invention can overcome problems of thetraditional pet coke, while promoting better combustion via oxidationcatalysts.

[1000] The ‘heavy’ transition metals (e.g. V, Ni, Fe, & Cu) in thefuel-grade coke of many refineries have been traditionally viewed asundesirable components. First, these transition metals, good oxidationcatalysts, promote the oxidation of sulfur dioxide to sulfur trioxide.Without dry scrubbing, higher sulfur trioxide concentrations causesignificantly higher flue gas dew points. The higher dew points causelower combustion efficiency due to higher stack temperatures and/orcold-end corrosion due to condensing sulfuric acid. Secondly, thesemetals, particularly vanadium and nickel, tend to form ash compounds(e.g. NiSO4 & vanadates) that have low melting points. In the hightemperature zones of the combustion system (e.g. boiler superheaters),these ash compounds become sticky, liquid materials that increase ashdeposits and cause high temperature corrosion.

[1001] As long as these problems are addressed, the heavy metals canprovide potential combustion improvements due to high oxidation catalystactivity. The high-temperature corrosion problems of traditional petcoke are partially due to char burnout near the furnace exit, raisingsuperheater tube metal temperatures. The modified pet coke of thecurrent invention mitigates this problem in several ways: (1) highlyporous coke promotes finer particle size distribution (i.e. HGI >80),(2) Higher VCM quantity and quality, and (3) oxidation catalyst activityof highly porous coke. All of these factors promote char burnout beforethe superheater tubes, potentially at lower excess air. As discussedpreviously, the impregnated sulfur reagents of the current invention caneffectively mitigate the formation of troublesome ash constituents andeffectively remove sulfur trioxides as well as sulfur dioxide.Consequently, modified coke of the current invention can effectivelymitigate the high-temperature corrosion, sticky ash deposition, andcold-end corrosion. Thus, the heavy metals can be effective oxidationcatalysts without the problems of traditional pet coke.

[1002] The activated, heavy metals in many petroleum cokes can promoteoptimal combustion by catalyzing various oxidation reactions. Asdiscussed previously, the adsorption character of the highly porous petcoke behaves as an oxidation catalyst in the coke char oxidation. As thecoke char oxidizes, the heavy metals, primarily vanadium and nickel, arereleased from the heavy coke compounds (e.g. porphyrins). Development oftheir multivalent ions activates their high oxidation catalyst activity.That is, their various oxidation states provide the bases of theircatalytic oxidation potential. These metal ions catalyze the coke charand sulfur oxidation at lower temperatures and/or lower excess airlevels. Furthermore, the metal ions released in the initial charoxidation can catalyze oxidation of VCMs in the flue gas, as well.Overall, these catalysts create greater oxidation at lower temperaturesand lower excess air levels, producing higher combustion efficiency andlower NOx emissions. Consequently, these metal oxidation catalysts canbe particularly helpful in low NOx combustion modes.

[1003] Optimizing the catalytic activity of the modified pet coke's‘heavy’ metals involves several factors. First, metals that are releasedin the early stages of combustion provide more benefits as oxidationcatalysts in the combustion zone. That is, the longer residence time inthe combustion zone may be desired. Thus, improved combustion of themodified coke can increase the oxidation catalyst activity, not only incoke char combustion, but in overall combustion, as well. Secondly,presence of certain types of chemicals (e.g. acids) can influence theoxidation states of the transition metals. Thus, the addition of certainchemicals can influence the strength of oxidation catalyst. Thirdly, thepresence of certain metal compounds in the ash can catalyze oxidationreactions downstream of the furnace high-temperature zones. Thus,promotion of these metal compounds, to the extent possible, canpotentially continue desirable oxidation reactions (e.g. char burnout)downstream of the furnace at lower temperatures. The optimal catalystactivity of the heavy metals in the modified coke will vary for eachcombustion system and its required operation, including heat transferand environmental requirements. Consequently, the optimization of metalscatalyst activity must evaluate the trade-offs of increased catalystactivity versus other impacts on the combustion system. One skilled inthe art can properly evaluate these trade-offs and make the appropriatemodifications to the factors, discussed above.

[1004] (5) Addition of Other Compounds:

[1005] Other types of chemical compounds can be added to further enhancethe modified pet coke of the current invention. As noted earlier,inorganic and organic compounds can be added to the modified pet cokevia the coke quench, either by adsorption or evaporative impregnation.That is, polar or ionic inorganic compounds can generally be added tothe modified pet coke due to their solubility in the coke quench water.After quench water evaporation, the inorganic compound is normally lefton the internal pores of the pet coke in molecular layers. Likewise,non-polar, organic compounds can be generally added to the modified petcoke via quench water. However, the deposition of this type of compoundis normally due to the modified pet coke's improved carbon adsorptioncharacter. Thus, various compounds from either broad class can beeffectively added to modified pet coke.

[1006] (6) General Issues for Impregnation of Modified Pet Coke:

[1007] The addition of any type of compounds to the modified cokerequires evaluation in each application. Proper consideration needs tobe given to the impacts of site-specific conditions, including localwater conditions, ambient temperatures, and coke quench & recyclesystems. In addition, there is considerable variation in the operatingconditions and procedures at the various delayed coker installations.Pressure effects, temperature effects, and the impact of operationalprocedures must be properly evaluated. Finally, special considerationmust be given to the combined effects, when adding more than onecompound. For example, there can be chemical reactions between injectedcompounds or the presence of another type of VCM or reagent can affectsolubility characteristics. One skilled in the art can make theseevaluations via engineering calculations and minor testing, if needed.Any necessary modifications can then be made within the spirit andintentions of the current invention.

[1008] C. Adsorption & Impregnation of Pet Coke: Enhanced Coke CarbonAdsorption

[1009] The ability to use the carbon adsorption character of themodified coke in various activated carbon applications was notedearlier. As discussed previously, the adsorption characteristics (e.g.pore structure and internal surface area) determine adsorptioncapacities and potential applications. The adsorption character can befurther enhanced by the addition of various chemical agents, based onthe desired application and performance. Various hydrocarbons and othernon-polar compounds can be added to the modified coke via adsorption.Similar to the sulfur reagents, other chemical agents can be added viaimpregnation. Both adsorption and impregnation are accomplished via thecoke quench of the decoking cycle. The adsorption and impregnation ofdesirable compounds are discussed below in further detail.

[1010] (1) Addition of Sulfur Compounds:

[1011] In the prior art, elemental sulfur has been added to activatedcarbon to enhance mercury removal capabilities. Apparently, theelemental sulfur chemically reacts with mercury via chemisorption invarious applications (e.g. coal boiler flue gas). The amount of sulfurimpregnated in the internal pores of the activated carbon is 10-20weight percent. The impregnation technique is apparently similar toother activated carbon impregnation. That is, soaking or spraying ofelemental sulfur onto the surfaces of the activated carbon is completedbefore drying. Drying is often performed in rotary kiln, fluid bed,multiple hearth, or vertical furnaces. The sulfur-impregnated activatedcarbon is then used to remove mercury in various vapor-phase andliquid-phase applications. For example, sulfur-impregnated activatedcarbon is injected into combustion flue gas at lower temperatures (e.g.350° F.) to remove mercury vapors.

[1012] In a similar manner, elemental sulfur can also be impregnated onthe internal surface of the modified pet coke of the current inventionto provide an alternative means of mercury removal. Elemental sulfur isanother by-product of crude oil processing, and already exists in aliquid form at most refineries. Soaking or spraying of elemental sulfur(from the refinery or otherwise) can be used to impregnate the surfacesof the modified coke, as well. That is, the refinery elemental sulfurcan be added to crushed pet coke of the current invention prior todrying in a suitable drier (e.g. rotary kiln, fluid bed, multiplehearth, or other drier).

[1013] Alternatively, the elemental sulfur could be added to themodified pet coke in the coke drum in a liquid or vapor form. The latteris preferable to prevent pluggage of pores and provide uniformdeposition of molecular layers on the pet coke's internal surface area.The refinery's liquid sulfur can be pumped to the coker via heated linesat the maximum practical temperature from the Claus Unit reactors. Thatis, less cooling in the condensers after the catalytic converters may bedesirable for better heat conservation. A special heater at the base ofthe coke drums can vaporize the elemental sulfurs at temperatures above830° F. The ultimate temperature would be dependent on the pressurerequired to inject the sulfur into the coke drum at the end of thecoking cycle. Prior to any steam out or cooling, the coke in the cokedrum is maintained at temperatures near the boiling point of theelemental sulfur (e.g. 830-850° F.). The vaporized sulfur would then beinjected into the bottom of the coke drum. Heater design would providesufficient heat to prevent premature condensation of sulfur in the petcoke. After sufficient sulfur impregnation, the modified pet coke iscooled in the decoking cycle in the normal manner, preferably withminimal to no steam-out prior to adding coke quench. Ideally, thesulfur, which is mostly insoluble in water, would be cooled to solidform (<230° F.) without significant entrainment of sulfur in the quenchwater. Realistically, some solid sulfur will be entrained in the quenchwater, and may require special treatment before quench water recycling.Excess sulfur impregnation can be required to make up for sulfurentrained in the quench water.

[1014] Obviously, this sulfur-impregnated modified coke would not beused as a fuel, but for specific mercury removal applications (e.g.boiler flue gas). The amount of impregnated sulfur would depend on theexisting sulfur content of the modified coke and its reactivity withmercury. In most cases, the existing coke sulfur (predominatelythiophenic sulfur) is not expected to react significantly with mercuryvapor, without combustion. Thus, the amount of impregnated elementalsulfur required for effective mercury removal is expected to be 5-25 wt.% (preferably 10-15 wt. %).

[1015] (2) Modified Coke with Other Chemisorption Agents:

[1016] Similarly, the modified coke of the current invention can beimpregnated with other chemical agents that remove targeted chemicalcompounds via chemisorption. These chemical agents should include, butshould not be limited to, iron oxide, manganese oxide, phosphoric acid,potassium carbonate, potassium iodide, potassium permanganate, silver,sulfur, sulfuric acid, triethylene diamine (TEDA), zinc oxide, and saltsof chromium, copper, or silver.

[1017] As noted before, various hydrocarbons and other non-polarcompounds can be added to the modified coke via adsorption. Similar tothe sulfur reagents, other chemical agents can be added viaimpregnation. Both adsorption and evaporative impregnation areaccomplished via the coke quench of the decoking cycle.

[1018] (3) Optimization of Catalyst Properties:

[1019] One of the primary uses of activated carbon is a catalyst orinert carrier material for catalytic agents. As discussed previously,activated carbon can perform well as an oxidation catalyst due to itsability to ionize molecular oxygen. In addition, activated carbon canprovide a key role in catalytic reactions as an inert carrier material.Typically, the catalytic agents are added to the activated carbon viaimpregnation techniques described earlier.

[1020] Similarly, the modified coke of the current invention can beimpregnated with various catalytic agents. These catalytic agents shouldinclude, but should not be limited to, transition metals, noble metals,mercury chloride, and zinc acetate. Again, various hydrocarbons andother non-polar compounds can be added to the modified coke viaadsorption. Similar to the sulfur reagents, other chemical agents can beadded via impregnation. Both adsorption and impregnation areaccomplished via the coke quench of the decoking cycle.

[1021] D. Other Applications of Adsorption/Impregnation Techniques;Enhanced Fuel & Carbon Adsorption Qualities

[1022] Processes and methods to improve the fuel properties, combustioncharacteristics, and other qualities of pet coke have been noted earlierin the current invention. This was accomplished by improving its carbonadsorption characteristics and using carbon adsorption technology to addcertain desirable fuel components in the delayed coking process. Thesesame processes and methods can be applied to other porous carbonaceousmaterials including (but not limited to) various coals, coal wastes,other cokes, and various activated carbons. For example, activatedcarbons that have served their useful lives in carbon adsorption systemscan be converted to high quality, solid fuels for disposal in solid fuelcombustion systems. That is, VCMs, SOx sorbents, oxygen content,oxidation catalysts, and other desirable fuel components can beuniformly integrated into the voids in these porous, carbonaceousmaterials. This can be accomplished by injecting these components intosuitable carrier media (e.g. water or air) which passes through theactivated carbons in the carbon adsorption bed or other vessel, afterone last regeneration cycle. Modification of the surface groups (e.g.oxygen surface groups) on the activated carbon may be necessary toadsorb polar, inorganic compounds. One skilled in the art of carbonadsorption technology can make the appropriate adjustments in theprescribed processes and methods of the current invention to achieve theoptimal levels of these desirable components to provide acceptable fuelcharacteristics.

[1023] The impregnation techniques of the current invention can also beused for impregnation of various chemical compounds in othercarbonaceous materials with adsorption characteristics. That is, aqueoussolutions in contact with other carbonaceous materials can provide themeans to impregnate sufficient quantities of various chemical compounds.Theses chemical compounds include, but should not be limited to VCMs,sulfur reagents, oxygen compounds, ionizing compounds, and catalysts.Again, modification of the surface groups (e.g. oxygen surface groups)on the activated carbon may be necessary to adsorb polar, inorganiccompounds.

[1024] For example, the activated carbon processes (e.g. rotary kiln)can use quench water to add molecular layers of various chemicalcompounds for improved adsorption, chemisorption, catalysis, etc. Thesame basic principles of the current invention apply to this process.Evaporation of saturated quench solution can leave desired solute on thesurface of activated carbon. However, the deposits can be primarily onthe external surface due to resistance to flow in the internal pores. Ifthis type of impregnation is not sufficient, pressurized soaking withsaturated or similar solutions prior to final drying may provide theneeded deposition on internal pores.

[1025] Another example of processing carbonaceous materials with aqueoussolutions is water washing of coals. In certain coals, the adsorptioncharacteristics can be sufficient to adsorb various types of VCMs in thewash water aqueous solution. Modification of the washing process (e.g.aqueous solution through bed of crushed coal) can enhance the adsorptionof VCMs. Similarly, sulfur reagents, oxygen compounds, and ionizingcompounds can be added with the proper solubility characteristics (e.g.Ca(OH)₂: more soluble at lower temperatures).

[1026] 7. Production of Premium Petroleum Coke: Optimized FuelEmbodiments

[1027] The various methods and embodiments of the present invention canalso be used to optimize combustion characteristics for specificcombustion applications. The following embodiment provides a means toproduce an upgraded petroleum coke that not only achieves the basicobjectives of this invention, but also optimizes fuel characteristics toreplace existing solid fuels with the least (or lower) amount ofequipment and operational modifications. As noted earlier, one fuel canbe directly substituted for an existing fuel in a full-scale operation,if the burning characteristics are sufficiently similar. As such, thevarious techniques, used in this invention to create a premium petroleumcoke, can be optimized in many cases to produce a direct replacementfuel for existing facilities. In this manner, a specific coker withcertain design, feedstocks, and refinery operational constraints can bemodified to produce a solid fuel with sufficiently similar combustioncharacteristics as the existing solid fuel at a specific combustionfacility.

[1028] As discussed previously, various pilot-scale and laboratory testscan effectively evaluate the burning characteristics for various fuels.Smaller scale tests to optimize parameters are preferable to full scaleoperations for various reasons, including economics and safety. In theexample for this embodiment, refinery pilot plant studies and modifiedB&W burning profile tests are used to optimize the burningcharacteristics of the upgraded petroleum coke. The B&W burning profiletests have been modified to incorporate differences in particle sizedistribution attributed to differences in the solid fuels' grindingcharacteristics. That is, a solid fuel with a higher HardgroveGrindability Index (HGI) is softer. An equivalent pulverizer can grindthese fuels to much finer particle size distributions with an equivalentgrinding energy. For example, coals with HGls of 50-70 are typicallyground to 65-80% through 200-mesh (˜74 microns). In contrast, theupgraded petroleum coke is expected to have HGIs of 90-120 and particlesize distribution of 80-95% through 200-mesh at the same (or less)grinding energy.

[1029] Pilot plant studies can be designed to find the optimalcombination of various techniques described in this invention to improvethe fuel qualities of petroleum coke. The following procedure canprovide an adequate means to optimize the petroleum coke fuelcharacteristics:

[1030] 1. Optimize design and operational parameters for the refinery'sdesalting system (or system parameters in other embodiments) to produceacceptable levels of sodium in coker feeds & coke.

[1031] 2. Optimize coker operating temperatures (or operating parametersof other embodiments, such as feedstock composition) to achievedesirable levels of sponge coke crystalline structure.

[1032] 3. Compare modified B&W burning profiles of the two fuels toevaluate adjustments in the quantity and quality of coke VCMs needed tonearly match the burning profile of the existing fuel.

[1033] 4. Optimize other coker operational parameters (e.g. oilysubstances in water quench) to adjust the quantity and quality of VCMsin the petroleum coke to obtain desirable combustion characteristics.

[1034] 5. Repeat steps 3 and 4 until the critical burningcharacteristics of the upgraded petroleum coke are sufficiently similarto the burning characteristics of the existing fuel.

[1035] 6. Reproduce optimal operating conditions in the refinery unitsto produce sufficient petroleum coke for a test burn in a pilot-scalecombustion system.

[1036] 7. Conduct test burn with upgraded coke and optimize combustiondesign and operational parameters. Modify burners or other equipment, asnecessary, to achieve acceptable combustion characteristics.

[1037] 8. Repeat steps 6 and 7 until evaluation of necessary equipmentand operational modifications is satisfactory. Implement equipment andoperational changes in the existing combustion facility.

[1038]FIG. 3 shows comparisons of burning profiles for existing coalsand petroleum coke. As noted earlier, some characteristics in theburning profile are not necessarily desirable, such as the blips forexcessive moisture and premature ignition. Other unobvious combustioncharacteristics (reflected in the burning profile's rate of release) areundesirable, including high ash content and low porosity char. Both ofthese hinder oxidation and the rate of release. Consequently, thecritical combustion characteristics in the burning profile are (1)ignition temperatures, (2) combustion intensity (height of maximumrelease rate), (3) total heat liberated (area under the profile), and(4) temperature of oxidation termination. If these parameters aresufficiently similar, the upgraded petroleum coke can readily replacethe existing fuel. The high char porosity, low ash content, low moistureand high HGI of the upgraded petroleum coke tend to shift the entiremodified burning profile to the left with only modest to moderateadditions of VCM. These properties of the upgraded petroleum coke arethe primary reason that this fuel can have better combustioncharacteristics than most coals, even with significantly lower (orcomparable) VCM content and/or quality.

[1039] In this manner, optimal levels of VCM quantity, coke crystallinestructure, VCM quality, and coke decontamination can be determined.After these levels are derived, the various methods and embodiments ofthe present invention (with proper consideration of various engineeringfactors) can be used to optimize the upgraded petroleum coke forspecific combustion applications. The optimized coker process controlprocedures (i.e. temperature controls, quench controls, etc.) viaburning profile tests is analogous to other coker process controls thatare determined by pilot plant tests.

[1040] In conclusion, the upgraded petroleum coke of the presentinvention can be readily optimized to provide sufficiently similar,critical combustion characteristics. In this manner, the upgradedpetroleum coke can readily replace solid fuels in existing combustionfacilities with limited modifications to current design and operation.Though the sulfur content does not significantly affect combustioncharacteristics, the optimization of upgraded petroleum coke that hasbeen desulfurized would provide an even more ideal fuel replacement.That is, the use of desulfurized coker feedstocks in this optimizationprocess can offer greater flexibility in the optimization ofenvironmental controls.

[1041] 8. Use of Premium Petroleum Coke: Conventional Boilers/WetScrubbers

[1042] Another embodiment of the present invention is the use of theupgraded petroleum coke in conventional, PC-fired utility boilers withtraditional particulate control devices and wet scrubbing systems. Thediscussion of this embodiment includes a basic description of aconventional utility boiler system with traditional particulate controldevices (electrostatic precipitators, baghouses, etc.), followed by awet scrubbing system for the removal of sulfur oxides and/orparticulates. The prior art has been modified with (1) a retrofitaddition of the flue gas conversion reaction chamber(s) and injectionsystem(s) and/or dry sorbent injection system(s). The primary differencefrom the exemplary embodiment is the presence of the wet scrubber. Thesuperior fuel characteristics of the upgraded petroleum coke areessentially the same as the exemplary embodiment for the followingsubsystems: fuel processing, combustion, heat transfer, and heatexchange. The environmental controls section is similar, including themodification of the existing particulate control device to a flue gasconversion system. However, the wet scrubber provides additionalflexibility in various options that can be used to optimize the levelsof control for particulates, sulfur oxides, carbon dioxide and otherundesirable flue gas components. For example, the operation of the wetscrubber can be used in combination with dry sorbent injection toincrease overall SOx removal efficiencies.

[1043] A. Conventional, PC Utility Boilers w/PCD & Wet Scrubber; ProcessDescription

[1044] In this embodiment of the invention, a conventional,pulverized-coal utility boiler with a traditional particulate controldevice is followed by a wet scrubbing system for the removal of sulfuroxides and/or particulates. The boiler and PCD systems are modified in amanner similar to the exemplary embodiment: conversion of sulfur oxidesto dry particulates upstream of the existing particulate controldevice(s). Thus, the prior art has been modified to achieve thisobjective with Option 1: dry reagent injection system(s) and/or Option2: a retrofit addition of flue gas conversion reaction chamber(s) andinjection system(s). FIG. 5 shows a basic process flow diagram for thissystem burning a pulverized solid fuel as the primary fuel. Auxiliaryfuel, such as natural gas or oil, is used for start-up, low-load, andupset operating conditions. The solid fuel 200 is introduced into thefuel processing system 202, where it is pulverized and classified toobtain the desired particle size distribution. A portion of combustionair (primary air) 204 is used to suspend and convey the solid fuelparticles to horizontally-fired burners 208. Most of the combustion air(secondary air) 210 passes through an air preheater 212, where heat istransferred from the flue gas to the air. The heated combustion air (upto 600° F.) is distributed to the burners via an air plenum 214. Thecombustion air is mixed with the solid fuel in a turbulent zone withsufficient temperature and residence time to initiate and completecombustion in intense flames. The intense flames transfer heat towater-filled tubes in the high heat capacity furnace 216, primarily viaradiant heat transfer. The resulting flue gas passes through theconvection section 218 of the boiler, where heat is also transferred towater-filled tubes, primarily via convective heat transfer. At theentrance to the convection section 218, certain dry reagents can bemixed with the flue gas to convert undesirable flue gas components (e.g.sulfur oxides) to collectible particulates (this embodiment: option 1).The reagents 220 pass through a reagent preparation system 222 and areintroduced into the flue gas via a reagent injection system 224. Steamor air 226 is normally injected through sootblowing equipment 228 tokeep convection tubes clean of ash deposits from the fuel and formed inthe combustion process. The flue gas then passes through the airpreheater 212, supplying heat to the combustion air.

[1045] The cooled flue gas then proceeds to the air pollution controlsection of the utility boiler system. At the exit of the air preheater,certain dry reagents can be mixed with the flue gas to convertundesirable flue gas components (e.g. sulfur oxides) to collectibleparticulates (this embodiment: option 1). The reagents 230 pass througha reagent preparation system 232 and are introduced into the flue gasvia a reagent injection system 234. The existing particulate controldevice 236 (ESP, baghouse, etc.) has been retrofitted with the additionof a reaction chamber 238 for this embodiment: option 2. Certainreagents (e.g. lime slurry) can be prepared in a reagent preparationsystem 240. The reagent(s) is dispersed into the flue gas through aspecial injection system 242. Sufficient mixing and residence time isprovided in the reaction chamber to convert most of the undesirable fluegas components (e.g. sulfur oxides) to collectible particulates. Theseparticulates are then collected in the existing particulate controldevice (PCD) 236. A bypass damper 244 is installed in the original fluegas duct to bypass (100% open) the retrofit flue gas conversion system,when necessary. The flue gas exits the PCD and enters the wet scrubbingsystem 246. The wet scrubbing system 246 removes additional SOx andparticulates. The clean flue gas then exits the stack 248.

[1046] B. Combustion Process of the Prior Art

[1047] The combustion process of the prior art for this embodiment issimilar to the combustion process of the prior art in the exemplaryembodiment.

[1048] C. Combustion Process of the Present Invention

[1049] The combustion process of the present invention for thisembodiment may be similar to the combustion process of the presentinvention in the exemplary embodiment. However, the higher density andspherical shape of the modified fluid petroleum coke make it moredifficult to burn than modified delayed coke. Consequently, certainparameters need to be adjusted to compensate for this undesirablecharacteristic. For example, a higher VCM specification (e.g. 20 wt. %VCM) can be necessary to achieve acceptable combustion characteristics.

[1050] D. Environmental Controls of the Prior Art

[1051] The environmental controls of the prior art for this embodimentmay be similar to the environmental controls of the prior art in theexemplary embodiment. Traditional particulate control devices (PCDs) forconventional, coal-fired utility boilers include (but should not limitedto) electrostatic precipitators (ESPs), various types of filteringsystems, and wet scrubber systems. Various wet scrubber systems haveevolved to control particulate and other emissions, including sulfuroxides. Wet scrubbing technologies range from simple flue gas scrubbingtowers to high pressure drop, turbulent mixing devices with downstreamseparation. As discussed previously. The most common type of wetscrubbers used for U.S. utility boilers is low-pressure drop spraytower. This type of wet scrubber system is included in this embodiment,and was described previously. The present invention does not claim novelwet scrubbing technology, but provides a novel application of suchtechnology that provides unexpected benefits and synergism. to optimizeenvironmental controls associated with the combustion of petroleum coke.Therefore, further description of readily available wet scrubbingtechnologies was not deemed appropriate, at this time.

[1052] E. Environmental Controls of the Present Invention

[1053] The present invention does not claim the conventionalenvironmental control technologies separately, but provides improvementsand novel combinations of these technologies in applications of thepresent invention. The different combinations of these technologies aresomewhat involved and provide synergism and/or unappreciated advantagesthat are not suggested by the prior art.

[1054] Similar to the exemplary embodiment, this embodiment describesthe use of existing particulate control equipment for the control ofsulfur oxides (SOx) and/or other undesirable flue gas components. Asnoted previously, fuel switching, from coal to the upgraded petroleumcoke of this invention, will make available a tremendous amount ofparticulate control capacity in existing particulate control devices.Again, the existing particulate control devices-PCDs (baghouses,electrostatic precipitators, etc.) can be used for extensive removal ofSOx and/or other undesirable flue gas components by converting them tocollectible particulates upstream of PCDs.

[1055] The primary difference in the environmental controls of thisembodiment (versus the earlier embodiments) is the presence of theexisting wet scrubber system. The existing wet scrubber increases thenumber of environmental control options and operational flexibility. Asthe final environmental control system before the flue gas exits thestack, the wet scrubber has additional impacts on environmentalemissions. The environmental controls of this embodiment (i.e. with thewet scrubber) are also applicable to upgraded petroleum coke from thedelayed and other coking processes.

[1056] (1) Particulates Impact:

[1057] The particulates impact of this embodiment may be similar to theearlier embodiments. That is, the fuel switch from coal to modifiedfluid coke will decrease the ash particulate loading by >90%. However,the additional wet scrubber system in this embodiment can provideadditional reduction of particulates but can also increase liquidentrainment in the flue gas that exits the stack. The degrees ofadditional particulate reduction and increase in liquid entrainment areexpected to be minor. Both are dependent upon the design and operationof the wet scrubber system.

[1058] (2) Sulfur Oxides Impact:

[1059] The sulfur oxides impact of this embodiment may be similar to theexemplary embodiment. However, as noted above, the existing wet scrubbersystem provides more options to achieve high levels of sulfur oxidescontrol. The existing wet scrubber also offers greater operationalflexibility and reliability, if a combination of sulfur oxide controlsis used.

[1060] In this embodiment, however, conversion of all the sulfur oxidesupstream of the PCD may not be desirable to optimize the combined sulfuroxides removal. In other words, a certain portion of the total sulfuroxides may be left unconverted and be collected downstream of theparticulate control device in the wet scrubbing system to maximize oroptimize the overall SOx removal. Alternatively, all the sulfur oxidesmay be converted to particulates and collected in the existingparticulate control device, avoiding the need for continuing theoperation of the wet scrubber. In these cases, the additional sulfurremoval may not be warranted, and the bypassing/shutdown of the wetscrubbing system can provide substantial savings in operating costs.Alternatively, the wet scrubber could then be converted to flue gasconversion technology for another undesirable flue gas component, suchas CO₂.

[1061] In Option 1 of this embodiment, dry sorbent injection systems areadded for additional control of sulfur oxides. As noted in the exemplaryembodiment, this unique application of this flue gas conversiontechnology is expected to achieve 50-70% SOx removal efficiency, on along-term basis. In this embodiment, however, the combination with theexisting wet scrubber system increases the overall sulfur oxidesremoval. That is, the existing wet scrubber typically has the capabilityof reducing the SOx FGCT outlet emissions by 80-95+%. The actual removalefficiency of the wet scrubber can be reduced slightly due to theeffects of lower SOx inlet concentrations. In conclusion, a combinationof this unique flue gas conversion retrofit and wet scrubber is expectedto achieve overall SOx removal efficiencies of 95-97% (e.g.0.7+0.85(.3)).

[1062] In Option 2 of this embodiment, retrofit reaction chamber(s) andreagent injection system(s) are added to convert sulfur oxides to dryparticulates upstream of the existing particulate control device(s).Since the combination of Option 1 and the existing wet scrubber areexpected to achieve such high SOx removal efficiencies (i.e. 95-97%),replacing Option 1 with Option 2 would usually not be cost effective.However, Option 2 can be effectively used, if shutting down or reducingthe load of the existing wet scrubber is desirable. In this case, thecombined SOx removal efficiency is expected to be the dry scrubberefficiency (e.g. 80-90%) plus the reduced efficiency of the existing wetscrubber multiplied by the remaining sulfur oxide emissions from theoutlet of the dry scrubber system.

[1063] In both flue gas conversion options, minor modifications may benecessary to maintain particulate collection efficiencies. Theparticulates coming into the existing PCDs may have substantiallydifferent properties than the particulates of the PCD's design basis.Consequently, modifications in design and/or operating conditions may berequired. For example, flue gas conditioning or operational changes maybe appropriate to achieve desirable resistivity characteristics, andmaintain collection efficiencies in existing electrostaticprecipitators.

[1064] (3) Carbon Dioxide Impact:

[1065] The carbon dioxide impact of this embodiment may be similar tothe exemplary embodiment. However, the wet scrubber system provides agreater opportunity to use the excess capacity of the existingparticulate control device for the control of carbon dioxide, instead ofsulfur oxides. In other words, the combination of the dry sorbentinjection (option 1) and the wet scrubber should be sufficient SOxcontrol to meet environmental regulations in most cases. Therefore, theretrofit addition of a flue gas conversion reactor/injection system(option 2) can be primarily used for carbon dioxide control.Alternatively, Option 2 can be used for SOx, and the wet scrubber couldthen be converted to flue gas conversion technology for carbon dioxide.This latter option would provide greater separation of technologies, andgreater conversion selectivity.

[1066] (4) Nitrogen Oxides Impact:

[1067] The nitrogen oxides impact of this embodiment may be similar tothe exemplary embodiment. However, the wet scrubber system can provideadditional reduction of nitrogen oxides. The overall impact is expectedto be relatively minor.

[1068] (5) Opacity Impact:

[1069] The opacity impact of this embodiment may be similar to theexemplary embodiment. However, the wet scrubber system can contributegreatly to increased opacity. That is, higher levels of liquidentrainment can induce the agglomeration of particulates and residualsulfur oxides, and increase opacity significantly over the exemplaryembodiment. Substantial reductions in ash particulates and sulfuroxides, in many cases, will offset the opacity increase due to liquidentrainment. Consequently, the liquid entrainment remains predominantlywater vapor (without impurities) and dissipates without visualobstruction when it leaves the stack.

[1070] (6) Soild Waste Impact:

[1071] The solid waste impact of this embodiment may be very similar tothe exemplary embodiment. However, any solid waste (e.g. sludge)generated by the use of the wet scrubber system must be addressed. Lowerutilization of the wet scrubber is expected to substantially reducesolid wastes from the wet scrubber. As noted earlier, reagent recyclingor regeneration with Options 1 or 2 can substantially reduce thequantity and/or quality of the solid wastes for disposal. For mostapplications, the solid wastes are expected to be substantially lessthan the existing system. Even their worst case scenarios will oftenproduce solid wastes no greater than the existing system.

F. EXAMPLE 2 Utility Boiler with PCD and Conventional Wet Scrubber

[1072] A power utility has a conventional, pulverized-coal fired utilityboiler that currently uses a high sulfur, bituminous coal (Illinois #6).This utility has a conventional particulate control device (PCD)followed by a wet scrubber, achieving ˜90% removal efficiency for sulfuroxides. Full replacement of this coal with a high-sulfur, fluid(petroleum) coke produced by the present invention would have thefollowing results:

[1073] Basis=1.0×10⁹ Btu/Hr Heat Release Rate as Input FuelCharacteristics Current Coal Upgraded coke Results VCM (% wt) 44.2 20.054% Lower Ash (% wt.) 10.8 0.3 97% Lower Moisture (% wt.) 17.6 3.8 78%Lower Sulfur (% wt) 4.3 5.2 21% Higher Heating Value (Mbtu/lb) 10.3 14.238% Higher Fuel Rate (MIb/Hr) 97.0 70.4 27% Lower

[1074] Pollutant Emissions: Uncontrolled/Controlled Ash Particulates(lb/MMBtu or MIb/Hr) 10.5/.53 .18/.01 98% Lower Sulfur Oxides (lb/MMBtuor MIb/Hr) 8.4/.84 7.4/.15 82% Lower Carbon Dioxide (lb/MMBtu or MIb/Hr)245 214 13% Lower

[1075] This example further demonstrates the beneficial application ofthe present invention. Again, the upgraded petroleum coke hassubstantially lower ash and moisture contents, compared to the existingcoal. These factors contribute greatly to (1) the ability to burnsuccessfully with lower VCM and (2) a fuel heating value that is 38%higher. In turn, the higher heating value requires a 27% lower fuel rateto achieve the heat release rate basis of one billion Btu per hour inthe boiler. As noted previously, this lower fuel rate and the softersponge coke significantly reduce the load and wear on the fuelprocessing system, while increasing pulverizer efficiency and improvingcombustion properties.

[1076] The ash particulate emissions (ash from the fuel) are 98% lowerthan the existing coal, due to the lower ash content and higher fuelheating value. Consequently, fuel switching to the upgraded cokeunleashes 97% of the capacity in the existing particulate controldevice. This excess capacity can now be used for the control of sulfuroxides via retrofit FGC technology.

[1077] Dry sorbent injection systems (this embodiment: option 1) isadded upstream of the existing particulate control device, along withany associated reagent preparation and control systems, for sulfuroxides control. In this case, the inlet SOx would be reduced by 70%(i.e. 7.4 to 2.2 Lb/MMBtu.). The existing wet scrubber can achieve anadditional 80-90% removal (i.e. 2.2 to 0.33 Lb/MMBtu.). Thus, thecombined control efficiency of the existing wet scrubber and theconverted PCD would be >95% (e.g. 0.7+0.85(0.3)). In this manner, theutility of converting the existing particulate control device to drysorbent injection represents 61% reduction in sulfur oxides (i.e. 0.33vs. 0.84 lb/MMBtu). This unexpected result is achieved even though thesulfur content (5.2%) of the upgraded petroleum coke is 21% higher thanthe sulfur level (4.3%) of the Illinois bituminous coal. If this levelof sulfur emissions is sufficient to meet environmental regulations, theretrofit addition of reaction chamber(s) and reagent injection system(s)is not necessary.

[1078] Alternatively, a SOx dry scrubber injection/reaction vessel (thisembodiment: option 2) can be added upstream of the existing particulatecontrol device, along with any associated reagent preparation andcontrol systems. This conversion of the existing particulate controldevice is assumed to achieve 90% reduction in sulfur oxides in thiscase. Therefore, the uncontrolled sulfur oxide emissions are reducedfrom 7.4 to 0.74 thousand pounds per hour. If the wet scrubber is stilloperated, an additional 75-85+% removal (i.e. 0.74 to 0.15 Lb/MMBtu) canbe achieved. Thus, the combined control efficiency of the existing wetscrubber and the converted PCD would be >98% (e.g. 0.9+0.8(.1)). In thismanner, the utility of converting the existing particulate controldevice to dry scrubbing represents over 82% reduction in sulfur oxides(i.e. 0.15 vs. 0.84 Ib/MMBtu). This unexpected result is achieved eventhough the sulfur content (5.2%) of the upgraded petroleum coke is 21%higher than the sulfur level (4.3%) of the Illinois bituminous coal.

[1079] In this example, the effective use of retrofit FGCTs foradditional reductions of carbon dioxide can be demonstrated. If option 1is used for sulfur oxides control, a FGCT injection/reaction vessel canbe added up stream of the existing PCD for additional carbon dioxidecontrol. In this case, the level of additional carbon dioxide control islimited by (1) the conversion of carbon dioxide to particulates and (2)the remaining capacity of the existing PCD without exceedingenvironmental regulations for particulate emissions. Alternatively,additional particulate control capacity could be added as part of theretrofit project. As noted earlier, the performance and capacity of theexisting PCD is not strictly on a mass weight basis, but depends onseveral factors, including particulate properties. If option 2 is usedfor sulfur oxide control, additional CO₂ control would likely be limiteddue to lack of selectivity of the FGCT reagent. In either case, theoriginal ash particulate capacity less the required capacity forconverted SOx (large ionic salts) may not leave sufficient capacity tomake CO₂ control cost effective. However, an upgraded petroleum cokethat has been desulfurized would offer even greater opportunities foradditional CO₂ control. As noted previously, the wet scrubber could alsobe converted to flue gas conversion technology for carbon dioxide.

[1080] This example also illustrates significant reductions in pollutantemissions, based solely on fuel switching. The 27% lower fuel rate ofthe upgraded petroleum coke greatly contributes to lower environmentalemissions of ash particulates, sulfur oxides, and carbon dioxide. The98% reduction in ash particulates, noted above, was primarily due tolower fuel ash concentration. However, uncontrolled emissions of sulfuroxides and carbon dioxide are significantly reduced primarily due to the27% lower fuel rate. That is, the sulfur content of the modified fluidcoke is 21% higher than the existing coal. Yet the upgraded petroleumcoke has 12% lower uncontrolled SOx. Similarly, the upgraded petroleumcoke has 20% higher carbon content (i.e. 82.8% vs. 69.0%). Yet theuncontrolled emissions of carbon dioxide is reduced by 13% due to fuelswitching. Similar results would be achieved by fuel switching to anupgraded petroleum coke from a delayed coking process.

[1081] Each utility boiler will have a different set of designconditions for converting the existing particulate control devices.Consequently, the degree of additional control needs to be determined ona case by case basis: including analyses of site-specific factors of thedesign and operation of the existing PCD. The conversion of each systemwill depend on various design and operational parameters. Engineeringfactors will determine the optimal design and level of control for SOxFGC technologies and wet scrubbing technologies. Again, the ultimatelevel of additional control for SOx and particulates will depend on (1)the efficiency of conversion of the sulfur oxides to particulates, (2)the efficiency of particulate collection, and (3) capacity limitationswithout exceeding environmental regulations for particulate emissions.9. Use of Premium “Fuel-Grade” Petroleum Coke: Additional Embodiments

[1082] Additional embodiments are described below for the various meansto effectively use the premium “fuel-grade” petroleum coke of thepresent invention. Any, all, or any combination of the embodiments,described above or below, could be used to achieve the objects of thisinvention. In any combination of the embodiments, the degree requiredcan be less than specified here due to the combined effects.

[1083] A. Combustion or Other End-User Systems: Additional Embodiments

[1084] (1) All Coal-Fired Boilers:

[1085] Further embodiments of the present invention would include theuse of upgraded petroleum coke in all types of coal-fired boilers (newor existing) regardless of furnace design, burner orientation, or otherdesign and operational parameters. These combustion systems wouldinclude, but should not be limited to, low heat capacity furnaces,cyclone furnaces, tangentially fired furnaces/burners, non-horizontalfired burners, etc.

[1086] (2) Other Combustion Applications:

[1087] Additional embodiments of the present invention would include allother facilities, where coals or petroleum cokes are currently used asfuels. The present invention should not be viewed as limited tocoal-fired utility boilers, but rather may be applicable to allcombustion applications, where the enhanced properties of the upgradedcoke provide improvements, combustion and otherwise. These combustionapplications may preferably include, but should not be limited to,industrial boilers, rotary kilns, cement kilns, process heaters,incinerators, and fluidized bed combustors. Also, the use of upgradedpetroleum coke as a supplemental fuel for these and other applicationsis anticipated by the present invention, including biomass and/or wastecombustion facilities.

[1088] (3) Coaucoke Gasification:

[1089] In other embodiments, the present invention anticipates the useof the upgraded petroleum coke in various coal/coke gasificationtechnologies. Coal gasification is a process that converts coal from asolid to a gaseous fuel (or chemical feedstock) through partialoxidation. Once the fuel (or chemical feedstock) is in the gaseousstate, undesirable substances, such as sulfur compounds and ash, can beremoved from the gas by established techniques. The net result is clean,transportable fuel (or chemical feedstock). Since coal/coke gasificationis a type of combustion (i.e. partial oxidation vs. full oxidation),many of the same principles discussed in the present invention stillapply. Consequently, many of the improved properties of the upgradedpetroleum coke would be desirable for partial oxidation. For example,the ability to optimize and control the quantity/quality of the VCM andthe coke crystalline structure can be very desirable for cokegasification. Also, the ability to decontaminate the coke in/prior tothe coking process can substantially reduce the gas clean-uprequirements. The dramatically lower levels of ash and sulfur indesulfurized petroleum coke of the present invention can significantlyreduce the capital and operating costs of the gasification process. Inthis manner, the upgraded petroleum coke can effectively replace variouscoals and cokes, partially or fully, in these gasification technologies.

[1090] (4) Magnetohydrodynamic Electric Generation:

[1091] The upgraded petroleum coke can be extremely valuable as apremium fuel for magnetohydrodynamic or MHD electric generation. The MHDprocess is currently under development. Conceptually, MHD electricgeneration occurs when hot, partially ionized combustion gases (plasma)are expanded through a magnetic field. This hot gas is produced in acoal combustor at temperatures approaching 5000° F. In order to achievethese temperatures, the combustion air must be preheated above 3000° F.The gas ionization is increased by seeding the gas with an easilyionized material, such as potassium compounds. The spent seed compoundsare treated and recycled for economic and environmental reasons. Themajor advantage of this technology is potential cycle efficiencies inexcess of 60%, compared to conventional cycle efficiencies of 35-38%.Achieving such high operating temperatures can be accomplished morereadily with the upgraded petroleum coke of the present invention. Theupgraded petroleum coke has substantially higher heating value, lowerash, and lower moisture content versus most coals. Also, the crystallinestructure of the upgraded petroleum coke has significantly higherporosity and can provide a finer fuel particle size distribution.Consequently, the upgraded coke can burn faster and cleaner, withminimal carbon residue. These properties potentially increase themaximum flame temperatures, as well. In addition, the quality andquantity of the VCM in the upgraded petroleum coke can be readilyformulated and controlled to optimize combustion properties and preventpremature combustion with very hot preheated air. Furthermore, the lowerash content can provide economic advantage in (1) the recovery/recycleof the seed compounds, (2) erosion prevention, and (3) environmentalcontrols. Finally, an upgraded petroleum coke that has been desulfurizedand/or demetallized can provide further advantages in this combustionsystem and environmental controls.

[1092] (5) Non-Combustion Applications:

[1093] Additional embodiments include any process that (1) uses coal orpetroleum coke for its physical and chemical properties (in addition toor regardless of its fuel value), and (2) is enhanced by theimprovements of the upgraded petroleum coke of this invention. Theseend-user applications include, but should not be limited to, cementkilns, coal/coke liquefaction, coal/coke cleaning or any process thatuses coal and/or coke as a raw material or chemical feedstock. Thepresent invention anticipates that the chemical and physical properties(as well as the fuel properties and combustion characteristics) of thenew formulation of petroleum coke will offer improved operations forthese types of applications. In these applications, the modifiedphysical and/or chemical properties may or may not be used inconjunction with the improved fuel properties and combustioncharacteristics.

[1094] B. Fuel Processing Improvements; Additional Embodiments

[1095] (1) More Than One Fuel Processing System:

[1096] In some cases, the petroleum coke end-user can have more than onefuel processing system. Site-specific design, operational, and/or otherconstraints may inhibit the fuel processing system benefits described inthe exemplary embodiment. For example, the facility may already have ordesire more than one fuel processing/management system. Similarly,certain refining operations and coking processes may not be capable ofproducing consistent fuels due to abnormal variations in operation andcoker feedstocks. Thus, modified fuel processing systems may berequired. In either case, the present invention still providessufficient utility in these situations and should not be limited.

[1097] (2) Modifications to Lower Sponge Coke Specifications:

[1098] In some cases, the petroleum coke end-user can modify the designor operation of the existing fuel processing system to reduce the“minimum-acceptable” sponge coke specification. These modificationsinclude (but should not be limited to) pulverizer type, capacity,number, and power usage characteristics. The present inventionanticipates these changes in an effort to (1) improve the operation andreliability of the combustion system and/or (2) reduce the degree ofchanges in the coker process. These modifications can be more costeffective in certain situations.

[1099] C. Combustion Improvements; Additional Embodiments

[1100] (1) Modifications to Lower VCM Specifications:

[1101] In some cases, the petroleum coke end-user can modify the designor operation of the existing combustion system to reduce the“minimum-acceptable” VCM specification. These modifications include (butshould not be limited to) burner design, burner number, aircontrols/distribution, furnace configuration, and boiler operation. Thepresent invention anticipates these changes in an effort to (1) improvethe operation and reliability of the combustion system and/or (2) reducethe degree of changes in the coker process. These modifications can bemore cost effective in certain situations.

[1102] (2) Modifications to Lower Sponge Coke Specifications:

[1103] In some cases, the petroleum coke end-user can modify the designand/or operation of the existing combustion system to reduce the“minimum-acceptable” sponge coke specification. These modificationsinclude (but should not be limited to) burner design, burner number, aircontrols/distribution, furnace configuration, and boiler operation. Thepresent invention anticipates these changes in an effort to (1) improvethe operation and reliability of the combustion system and/or (2) reducethe degree of changes in the coker process. These modifications can bemore cost effective in certain situations.

[1104] (3) Modifications to Avoid Coke Decontamination:

[1105] Another embodiment of the present invention would modify thecombustion systems or operations of the petroleum coke user, and avoidthe need for coke decontamination. Some combustion system modifications,including modified firing techniques, firebox temperature profiles, andcombustion equipment design/operation can alleviate the detrimentaleffects of certain salts and metals.

[1106] (4) New Designs that Avoid Coke Decontamination:

[1107] Another embodiment of the present invention anticipates newdesigns for combustion systems with combustion, heat exchange, and airpollution control systems that are capable of handling the detrimentaleffects of the petroleum coke contaminants, including sulfur. Thus, theneed for petroleum coke decontamination can be avoided.

[1108] D. Heat Exchange Improvements; Additional Embodiments

[1109] (1) Modifications to Avoid Coke Decontamination:

[1110] Another embodiment of the present invention would modify the heatexchange equipment design or operation of the petroleum coke user'sfacility. Some modifications in heat exchange equipment design and/oroperation can alleviate the detrimental effects of certain mineraldeposits (e.g. salts and metals). These modifications include (butshould not be limited to) better tube metallurgy, increased soot blowingfrequency, heat transfer temperature profiles, and heat transferequipment design/operation. These modifications, with or without thecombustion system modifications, may reduce or eliminate the need forpetroleum coke decontamination.

[1111] (2) No Coke Decontamination Required:

[1112] Another embodiment of the present invention would selectively usethe upgraded petroleum coke in existing combustion, heat exchange andair pollution control systems that are currently capable of handling thedetrimental effects of the petroleum coke contaminants without cokedecontamination.

[1113] E. Environmental Controls; Additional Embodiments

[1114] The new formulation of petroleum coke can provide improvedenvironmental benefits for a wide variety of solid-fuel applications,both existing and new. The predominant environmental control feature ofthe present invention is creating and converting excess capacity in theexisting particulate control device. This excess capacity can be usedfor effective control of undesirable flue gas components by convertingthem to collectible particulates upstream of the existing particulatecontrol device. The pollutants, which are controlled in this manner,would include (but not be limited to) sulfur oxides, nitrogen oxides,carbon dioxide, metals, and air toxics. Other pollutants, defined now orin the future, could also be controlled in this fashion. The newformulation of petroleum coke makes this unique retrofit controlpossible. In addition, the environmental issues for all embodiments areapplicable regardless of the source of the upgraded petroleum coke (e.g.delayed coking & fluid coking).

[1115] (1) Other Flue Gas Conversion Technologies:

[1116] Various types of technologies can be used for the conversion ofgases or liquids to collectible particulates (dry or wet) upstream ofthe existing particulate control devices. The exemplary and secondaryembodiments discussed the novel application of several proven, flue gasconversion technologies that convert sulfur oxides to dry particulates.These embodiments also noted developing technologies for the conversionof carbon dioxide to collectible particulates. The present inventionanticipates further development of these and other technologies toconvert SOx and CO₂. These technologies may include different reagents,reagent preparation, and reagent injection systems. The presentinvention also anticipates the development of other technologies for theconversion of nitrogen oxides, air toxics, and other pollutants. Theconversion of air toxics, such as heavy metal vapors (e.g. mercury), isan area of great potential in the future.

[1117] (2) Existing Dry Scrubber:

[1118] Another embodiment of the present invention is solid-fuelcombustion systems with an existing dry scrubbing system, new orotherwise. An existing dry scrubber can be modified to use existingparticulate control capacity for additional control of undesirable fluegas components, particularly sulfur oxides. The reagent injection andsubsequent reaction zones would need to be modified to provide for (1)greater injection rates, (2) adequate mixing, and (3) comparableresidence time. The optimal application of these technologies forsite-specific situations can be determined through evaluation of theengineering factors involved.

[1119] (3) Desulfurization and/or Demetallization of the Upgraded Coke.

[1120] Another embodiment of the present invention that would improveenvironmental emissions is the desulfurization and/or demetallization ofthe upgraded petroleum coke. As noted above, there are various methodsto decontaminate the new formulation of petroleum coke. Any method thatdecreases the sulfur content will decrease the sulfur oxides emissions.In turn, this can make any excess capacity in the existing particulatecontrol devices (including wet scrubbers) available for other types ofenvironmental control (e.g. flue gas conversion of CO₂). Similarly, anydemetallization can decrease the emissions of metals, particularly thosethat exit the combustion process in vapor form (e.g. mercury andvanadium oxides). EXAMPLE 4 demonstrates the effective use ofdesulfurized petroleum coke. Note its impact on the sulfur oxidesemissions and the increased ability to use excess PCD capacity forcarbon dioxide control. In addition, desulfurization and/ordemetallization of the upgraded petroleum coke can alleviate the needfor high efficiency desalting. As discussed previously, very low levelsof sodium are not as critical, if sulfur and vanadium levels aresufficiently low. Furthermore, certain types of desulfurization and/ordemetallization of upgraded coke can produce very low levels of sodiumwithout extensive desalting. In either case, very low sodium levels arestill preferable, unless their achievement becomes incompatible withother objectives.

[1121] (4) No Change in the Existing Environmental Control System(s):

[1122] Another embodiment of the present invention would selectively usethe upgraded petroleum coke in existing combustion/air pollution controlsystems (e.g. ESP & wet scrubber) that are currently capable of handlingthe level of sulfur in the upgraded petroleum coke of the presentinvention. Many environmental regulations have pollution control limitsfor sulfur oxides, written in pounds per million Btu heat release of thefuel. Consequently, petroleum coke with a higher concentration of sulfurcan be substituted for a coal with lower sulfur concentration withoutexceeding the regulatory limits. EXAMPLES 1-4 demonstrate this aspect ofthe present invention. The sulfur content of the upgraded petroleum cokeis equal to or greater than the coals' sulfur contents. Yet theuncontrolled SOx emissions from the upgraded petroleum coke are less.This alternative is possible due to the 15-25% higher heat content ofpetroleum coke compared to most coals (e.g., 13-15,00 Btu/lb vs.10.5-13,000 Btu/lb for bituminous coal) and its subsequent lower fuelrate.

[1123] (5) Recycling of Flue Gas Conversion Reagents:

[1124] Another embodiment of the present invention would includeextensive recycling of unreacted reagents in the FGCT systems, thatconvert flue gas components to collectible particulates. Prior art ofSOx dry scrubber technology currently recycles collected flyash into thereagent injection to increase reagent usage. However, high ashparticulates of existing fuels limit the degree of recycling. Theupgraded petroleum coke of the present invention has such low ashparticulates that greater quantities of collected flyash can beeffectively recycled to increase reagent utilization efficiencies.Increased reagent utilization efficiencies would increase the SOxcontrol efficiency and reduce the solid wastes requiring disposal. In asimilar manner, the present invention can improve other flue gasconversion technologies, as well.

[1125] (6) Regeneration of Flue Gas Conversion Reagents:

[1126] Another embodiment of the present invention involves theregeneration of spent reagent in flue gas conversion technologies. Thisregeneration can substantially reduce the make-up reagent and wastedisposal required. The regeneration process can include, but should notbe limited to, hydration of the collected flyash and subsequentprecipitation of the undesired ions (i.e. sulfates, carbonates, etc.).In cases where slaked lime is used as the conversion reagent, theregeneration process can greatly reduce the carbon dioxide generated inthe reagent preparation process: limestone (calcium carbonate—CaCO₄) tolime (calcium oxide—CaO). Furthermore, the regeneration process wouldlikely include a purge stream to remove unacceptable levels ofimpurities from the system. This purge stream would be analogous to blowdown streams in many boiler water and cooling water systems. In manycases, this purge stream will contain a high concentration of heavymetals, including vanadium. Various physical and/or chemical techniquescan be used to extract and purify these metals for commercial use.Finally, the ability to continually regenerate reagents provides theopportunity to improve the flue gas conversion process through the useof exotic reagents; not considered previously due to costs. In thismanner, the regeneration of conversion reagents can (1) substantiallyreduce reagent and flyash disposal costs, (2) reduce C0₂ emissions, (3)create a resource for valuable metals, and (4) provide the means toeconomically improve the flue gas conversion process via the use of moreexotic reagents.

[1127] (7) Salable By-Products from Fgc Technologies:

[1128] Another embodiment of the present invention improves the qualityof flue gas conversion products to provide salable by-products andsubstantially reduce the solid wastes requiring disposal. The extremelylow ash particulate levels (i.e. low impurities) provide greateropportunity to use the collected flyash as raw materials for variousproducts, instead of solid waste requiring disposal. These productsinclude, but are not limited to, gypsum wallboard and sulfuric acid.

[1129] (8) Collection of Carbon Dioxide Generated in ReagentPreparation: Another embodiment of the present invention anticipates thedevelopment of carbon dioxide collection systems for the CO₂ released asa gas in the reagent preparation systems for flue gas conversiontechnologies. For example, most SOx dry scrubber systems convert calciumcarbonate to calcium oxide and carbon dioxide, that currently goesdirectly to the atmosphere. The CO₂ collection technologies can include(but should not be limited to) activated carbon adsorbtion with pressureswing regeneration. The upgraded petroleum coke of the present inventionhas many desirable properties (e.g. high porosity, high HGI, etc.) foruse as the activated carbon in this CO₂ collection process. That is,upgraded petroleum coke can be readily altered to be effectively used inthis carbon adsorption application. The activated coke eventually losesactivation after numerous cycles of use and regeneration. Thedeactivated coke can then be blended into the coke fuel and subsequentlyburned in the combustion system.

[1130] (9) Integration of Activated Coke Removal Technologies:

[1131] Combined control of SOx and NOx emissions has been commerciallyachieved in Germany and Japan using sorbent beds of activated coke oractivated char in the flue gas stream. The activated coke/char canadsorb SO₂ and catalyze the reduction of NOx to nitrogen gas by ammoniainjection. SO₂ removals of 90-99+% and NOx removals of 50-80+% have beenreported for low- to medium-sulfur systems. An additional advantage ofthis system is noted to be the adsorbtion of air toxics and carbondioxide to a limited extent. High coke consumption and high moisturecontent are noted to be potential problems, particularly in high-sulfurapplications. The present invention anticipates effective integration ofthis technology. Similar to the previous embodiment, the upgraded cokeof the present invention has many desirable characteristics of theactivated carbon. In many cases, the upgraded coke can be readilymodified to be effectively used as the activated coke. Again, the cokeloses activation after numerous cycles of use and regeneration.Apparently, this occurs more quickly in the high-sulfur applications.Deactivated coke can then be blended into coke fuel and subsequentlyburned in the combustion system.

[1132] In a similar manner, the upgraded coke of the present inventioncan be used for activated carbon technologies for the removal of airtoxics (e.g. mercury), carbon dioxide, or other undesirable flue gascomponents. The activated carbon technologies for these componentssystem can be integrated (1) fully into the SOx/NOx activated cokesystem (to the extent possible), (2) share auxiliary systems, or (3)work independently with or without the SOX/NOx activated coke system. Inany case, deactivated coke can be blended into the coke fuel andsubsequently burned in the combustion system.

F. EXAMPLE 3 Low-Sulfur Liqnite Coal vs. Medium Sulfur Coke with DrySorbent Injection

[1133] Another power utility has a conventional, pulverized-coal firedutility boiler that currently burns a low-sulfur, lignite coal fromTexas. The existing utility has a large-capacity, particulate controldevice with no sulfur oxides control. Full replacement of this coal witha medium-sulfur, petroleum coke produced by the present invention wouldhave the following results:

[1134] Basis=1.0×10⁹ Btu/Hr Heat Release Rate as Input FuelCharacteristics Current Coal Upgraded coke Results VCM (% wt) 31.5 16.049% Lower Ash (% wt.) 50.4 0.3 99+% Lower Moisture (% wt.) 34.1 0.3 99+%Lower Sulfur (% wt) 1.0 2.5 150% Higher Heating Value (Mbtu/lb) 3.9 15.3290% Higher Fuel Rate (MIb/Hr) 254 65.4 74% Lower

[1135] Pollutant Emissions: Uncontrolled/Controlled Ash Particulates(lb/MMBtu or 128/6.4 0.2/.01 99+% Lower MIb/Hr) Sulfur Oxides (lb/MMBtuor MIb/Hr) 5.1 3.2/.96 37/81% Lower Carbon Dioxide (lb/MMBtu or 315210/150 33/52% Lower MIb/Hr)

[1136] This example further demonstrates the beneficial application ofthe present invention. Again, the upgraded petroleum coke hassubstantially lower ash and moisture contents, compared to the existingcoal. These factors contribute greatly to (1) the ability to burnsuccessfully with lower VCM and (2) a fuel heating value that is 290%higher. In turn, the higher heating value requires a 74% lower fuel rateto achieve the heat release rate basis of one billion Btu per hour inthe boiler. As noted previously, this lower fuel rate and the softersponge coke substantially reduce the load and wear on the fuelprocessing system, while increasing the pulverizer efficiency andimproving combustion characteristics.

[1137] The ash particulate emissions (ash from the fuel) are >99+% lowerthan the existing coal, due to the lower ash content and higher fuelheating value. Consequently, fuel switching to the upgraded cokeunleashes >99% of the capacity in the large, existing particulatecontrol device. Part of this excess capacity can now be used for thecontrol of sulfur oxides via retrofit SOx FGC technology.

[1138] In this example, dry sorbent injection into the combustion systemwith the excess capacity of the existing PCD is sufficient to achievethe desirable sulfur oxides control. Dry sorbent is injected in thefirebox and downstream of the air preheater to achieve 70% SOx removal.Therefore, the uncontrolled sulfur oxide emissions are reduced from 3.2to 0.96 thousand pounds per hour. In this manner, the utility ofconverting the existing particulate control device to dry sorbentinjection represents 81% reduction in sulfur oxides (i.e. <0.96 vs. 5.1lb/MMBtu). This unexpected result is achieved even though the sulfurcontent (2.5%) of the upgraded petroleum coke is only 150% higher thanthe sulfur level (1.0%) of the Texas lignite coal.

[1139] In this example, carbon dioxide is reduced by the lower fuel rateand new flue gas conversion technologies (FGCT). The 74% lower fuel ratealone reduces the carbon dioxide emissions by 32%. FGCT processesconvert carbon dioxide to dry solid particulates that can be collectedin the conventional particulate control device. The retrofit deploymentof FGC technology can be limited by the excess capacity in the existingPCD. However, the remaining part of the excess capacity is expected toprovide further reductions of carbon dioxide; at least 60 Mlb/Hr. Inthis case, the additional CO₂ control from FGCT increases the combinedreduction to >50%.

[1140] This example also demonstrates that the beneficial application ofthe present invention does not necessarily require the conversion ofexisting particulate control devices. Based solely on fuel switching,(74% lower fuel rate and the >99% lower ash content of the upgradedpetroleum ) substantially lower environmental emissions of ashparticulates, sulfur oxides, and carbon dioxide are achieved. Ashparticulates are reduced by 99%. The uncontrolled SOx emissions are 37%lower, even though the sulfur content of the upgraded petroleum coke is150% higher. Similarly, the uncontrolled carbon dioxide emissions arereduced by 32%, even though the carbon content of the upgraded petroleumcoke is 163% higher (i.e. 88.8% vs. 33.8%). All of these pollutantemission reductions are achieved without conversion of the existing PCD.They come solely from switching fuel to the new formulation of petroleumcoke of the present invention.

G. EXAMPLE 4 Low Sulfur Western Coal vs. Desulfurized Petroleum Coke

[1141] Another utility has a conventional, coal-fired utility boilerthat currently uses a very low sulfur, sub-bituminous coal from Montana.This utility has a typical particulate control device (PCD) with nosulfur oxides emission control. Full replacement of this coal with adesulfurized (85%) petroleum coke produced by the present inventionwould have the following results:

[1142] Basis=1.0×10⁹ Btu/Hr Heat Release Rate as Input FuelCharacteristics Current Coal Upgraded coke Results VCM (% wt) 40.8 16.061% Lower Ash (% wt.) 5.2 0.3 94% Lower Moisture (% wt.) 23.4 0.3 99%Lower Sulfur (% wt) 0.44 0.65 48% Higher Heating Value (Mbtu/lb) 9.515.3 61% Higher Fuel Rate (MIb/Hr) 105 65.4 38% Lower

[1143] Pollutant Emissions: Uncontrolled/Controlled Ash Particulates(lb/MMBtu or MIb/Hr) 5.5/.3 0.2/.01 97% Lower Sulfur Oxides (lb/MMBtu orMIb/Hr) 0.92 0.85  8% Lower Carbon Dioxide (lb/MMBtu or MIb/Hr) 277210/190 23/31% Lower

[1144] This example further demonstrates the beneficial application ofthe present invention. Again, the upgraded petroleum coke hassubstantially lower ash and moisture contents, compared to the existingcoal. These factors contribute greatly to (1) the ability to burnsuccessfully with lower VCM and (2) a fuel heating value that is 61%higher. In turn, the higher heating value requires a 37% lower fuel rateto achieve the heat release rate basis of one billion Btu per hour inthe boiler. As noted previously, this lower fuel rate and the softersponge coke substantially reduce the load and wear on the fuelprocessing system, while increasing the pulverizer efficiency andimproving combustion characteristics.

[1145] In this example, the desulfurized petroleum coke of the presentinvention is sufficient to achieve very low sulfur oxide emissions(<1.25 lb/MMBtu). In fact, the desulfurized coke achieves 8% loweremissions (i.e. 0.85 vs. 0.92 lb/MMBtu) than this very low sulfur,western coal, even though the desulfurized coke has 50% higher sulfurcontent. Consequently, the excess capacity created in the particulatecontrol is available for other undesirable flue gas components via FGCtechnologies.

[1146] Carbon dioxide FGC technologies with the excess capacity of theexisting PCD are expected to provide increased reductions in carbondioxide. The ash particulate emissions (ash from the fuel) are >97%lower than the existing coal, due to the lower ash content and higherfuel heating value. Consequently, fuel switching to the upgraded cokeunleashes >97% of the capacity in the existing particulate controldevice. This excess capacity can now be used for the control of carbondioxide via retrofit FGC technology. Carbon dioxide FGCT reagent(s)injection/reaction vessel is added upstream of the existing particulatecontrol device, along with any associated reagent preparation andcontrol systems. The retrofit of this technology can be limited by theexcess capacity in the existing PCD. However, the excess capacity isexpected to provide further reductions of carbon dioxide; at least 20Mlb/Hr or 7%. In this case, the combined effect of fuel switching andcarbon dioxide FGCT is 30+% reduction in CO₂ (190 vs. 275 Mlb/hr).

[1147] The desulfurized coke can be used to make most of the excess PCDcapacity (created from fuel switching) available for uses other than SOxcontrol. As shown in Example 3, greater reductions of C0₂ can beexpected from retrofit FGC technology, if the current coal has higherash content and lower heating values. In this manner, additionalbenefits from switching to desulfurized, premium “fuel-qrade” petroleumcoke can be achieved in those applications.

H. EXAMPLE 5 Mixture of Existing Coal & Upgraded Petroleum Coke w/DrySorbent Injection

[1148] Another power utility has a conventional, pulverized-coal firedutility boiler that currently burns a medium-sulfur, bituminous coalfrom western Pennsylvania (i.e. Pittsburgh #8). The existing utilitycurrently has a typical particulate control device with no sulfur oxideemissions control. Replacement of half of this coal (i.e. 50% by weight)with a high-sulfur petroleum coke produced by the present inventionwould have the following results:

[1149] Basis=1.0×10⁹ Btu/Hr Heat Release Rate as Input FuelCharacteristics Current Coal 50/50 Coal/Coke Results VCM (% wt) 40.228.1 32% Lower Ash (% wt.) 9.1 4.7 48% Lower Moisture (% wt.) 5.2 2.846% Lower Sulfur (% wt) 2.3 3.3 43% Higher Heating Value (Mbtu/lb) 12.513.9 11% Higher Fuel Rate (MIb/Hr) 79.7 72.6  9% Lower

[1150] Pollutant Emissions: Uncontrolled/Controlled Ash Particulates(lb/MMBtu or Mlb/Hr) 7.3/0.7 3.8/0.4 43% Lower Sulfur Oxides (lb/MMBtuor Mlb/Hr) 3.7/3.7 4.7/1.4 62% Lower Carbon Dioxide (lb/MMBtu or Mlb/Hr)216 210  3% Lower

[1151] This example further demonstrates the beneficial application ofthe present invention. The 50%/50% mixture of the existing coal andupgraded petroleum coke has significantly lower ash and moisturecontents, compared to the existing coal. These factors contributegreatly to (1) the ability to burn successfully with lower VCM and (2) afuel heating value that is 11% higher. In turn, the higher heating valuerequires a 9% lower fuel rate to achieve the heat release rate basis ofone billion Btu per hour in the boiler. As noted previously, this lowerfuel rate and the softer sponge coke substantially reduce the load andwear on the fuel processing system, while increasing the pulverizerefficiency and improving combustion characteristics.

[1152] The ash particulate emissions (ash from the fuel) are >43% lowerthan the existing coal, due to the lower ash content and higher fuelheating value. Consequently, fuel switching to the upgraded cokeunleashes >43% of the capacity in the existing particulate controldevice. This excess capacity can now be used for the control ofundesirable flue gas components via FGC technology.

[1153] In this example, dry sorbent injection into the combustion systemwith the excess capacity of the existing PCD is sufficient to achievethe desirable sulfur oxides control. Dry sorbent is injected in thefirebox and downstream of the air preheater to achieve 70% SOx removal.Therefore, the uncontrolled sulfur oxide emissions are reduced from 4.7to 1.4 thousand pounds per hour. In this manner, the utility ofconverting the existing particulate control device to dry sorbentinjection SOx FGCT represents 62% reduction in sulfur oxides (i.e. 1.4vs. 3.2 lb/MMBtu). This unexpected result is achieved even though thesulfur content (3.3 wt. %) of the coal/coke mixture is 43% higher thanthe sulfur level (2.3%) of the existing coal.

[1154] 10. Use of Premium “Fuel-Grade” Pet Coke: Optimized EnvironmentalEmbodiment

[1155] The various methods and embodiments of the present invention,used to control environmental emissions, can also be used to optimizethe overall environmental controls for specific combustion applications.In this manner, an existing combustion facility can be modified toproduce the optimal combination of environmental controls to meet orexceed environmental regulations. The following embodiment provides ameans (1) to produce an upgraded petroleum coke that not only achievesthe basic objectives of this invention, but (2) to also optimize thevarious environmental control options for various undesirable flue gascomponents and solid wastes.

[1156] As noted earlier, the upgraded petroleum coke of the presentinvention has unique combustion characteristics that provides for novelcombinations of environmental control technologies. That is, much lowerash particulates and lower fuel rates of the upgraded petroleum cokecreates tremendous capacity in the existing particulate control deviceto use for the collection of various undesirable flue gas components.However, the undesirable flue gas components must be converted tocollectible particulates (dry, wet, or otherwise) upstream of theexisting particulate control device (PCD). Consequently, the level ofcontrol for each undesirable flue gas component will depend on severalfactors: (1) Net availability of PCD capacity, (2) Effectiveness ofconversion to collectible particulates, (3) Characteristics ofconversion reagents: Selectivity, reactivity, chemical complexity, etc,and (4) Reaction characteristics: temperature, residence time, andmixing requirements. The selectivity of the conversion reagent is a keyaspect, when trying to control specific undesirable flue gas components.Otherwise, the reagent will be wasted on components that are notintended for conversion to collectible particulates (e.g. carbon dioxideversus sulfur oxides).

[1157] Pilot plant studies can be designed to determine the appropriatecombination of various techniques described in this invention tooptimize the control of various undesirable flue gas components. Thefollowing procedure can provide an adequate means to optimize the novelcombinations of environmental controls of the present invention in anexisting combustion facility:

[1158] 1. Create PCD Capacity; Reduction in Ash Particulates and FuelRate Due to Fuel Switching:

[1159] a. Analyze PCD capacity created: PCD design and operatingparameters

[1160] Calculate increase in collection area/flue gas ratio; due todecrease in flue gas flow rate

[1161] Determine available capacity, based on differences in particulatecollection characteristics

[1162] b. Evaluate potential for particulate conversion technologies w/oexceeding particulate regulations

[1163] 2. Control of Undesirable Flue Gas Components: SOx, NOx, CarbonDioxide, Air Toxics, Metals, etc.

[1164] a. Determine level of control required for each undesirable fluegas component

[1165] b. Prioritize undesirable flue gas components (e.g. SOx, CO₂,NOx, air toxics, etc.)

[1166] c. Evaluate control options for each undesirable flue gascomponent

[1167] Fuel replacement only: Lower fuel rate and better combustioncharacteristics

[1168] Reagent injection in the furnace and/or downstream heat exchange

[1169] Retrofit reaction chamber with reagent injection and mixingsystems

[1170] Coker feedstock decontamination and/or treatment(s) of upgradedpetroleum coke

[1171] Combination of above and/or other control options

[1172] d. Integrate all possible control combinations into variouscontrol scenarios

[1173] e. Optimize various control scenarios to achieve controlobjectives at lowest cost

[1174] This optimization process is unique for each specific combustionfacility, and can become quite complex and time-consuming. First of all,the process must take into account many site-specific factors, including(1) design and operation of the existing combustion facility andparticulate control devices and (2) characteristics of the existing fueland the replacement upgraded petroleum coke fuel. Secondly, theoptimization process must carefully consider the relative impacts of theindividual control systems on each other, when combined in a controlscenario. For example, the reagents to convert undesirable flue gascomponents to collectible particulates may interfere with each other.Alternatively, they can create undesirable compounds (e.g. ammoniumbisulfate from reagent ammonia) that can foul, plug, or corrodedownstream system components. Finally, the mix of various collectibleparticulates (e.g. calcium sulfates, ammonium bicarbonates, etc.) caninhibit the effective use of reagent (flyash) recycling/regeneration toimprove reagent utilization and reduce solid waste disposal. Some ofthese principles are illustrated in the following embodiment of maximumenvironmental protection.

[1175] The embodiment of maximum environmental protection would likelyinclude desulfurization and demetallization of the upgraded petroleumcoke and convert excess particulate control capacity in the existingsystem for additional removal of various undesirable flue gascomponents.

[1176] 1. Sulfur Oxides (SOx): Though most of the sulfur (e.g. >85%)would be removed in the hydrodesulfurization of the coker feedstocks,additional control of sulfur oxides can be completed by injection ofreagents in the furnace and downstream heat exchange. In this manner,50-70% of the remaining SOx could be converted to collectibleparticulates, or >93% total reduction.

[1177] 2. Carbon Dioxide (CO₂): In this embodiment, C0₂ is given secondpriority for available PCD capacity. Carbon dioxide would likely beconverted to collectible particulates via retrofit reaction chamber(s)with reagent injection and mixing systems. Reaction efficiency andavailable PCD capacity would primarily limit the level of CO₂ removal.Additional PCD capacity could be added as part of the retrofit project.Regeneration and recycle of conversion reagents would likely broaden C0₂conversion options and improve economic viability.

[1178] 3. Air Toxics: Most of the air toxic emissions associated withcombustion processes are related to the heavy metals (e.g. mercury,vanadium, nickel, etc.) in the fuel. These air toxics could also beconverted to collectible particulates, as long as their conversionreagents are compatible and do not interfere with the conversionreagents for the SOx and CO₂. However, the hydrodesulfurization of cokerfeedstock will also decrease the metals content of the coke.Consequently, the consumption of available PCD capacity for air toxicsremoval is not expected to be significant.

[1179] 4. Nitrogen Oxides (NOx): The nitrogen content of petroleum cokeis normally reduced by the hydrodesulfurization of the coker feed.Nitrogen oxides are further reduced by the lower fuel rates of thepetroleum coke. Furthermore, the dramatically lower ash, which isresponsible for more uniform and stable flame, makes the upgradedpetroleum coke more susceptible to Low NOx burner designs for loweremissions of nitrogen oxides (NOx). The remaining NOx could also beconverted to collectible particulates, but selective noncatalyticreduction (SNCR) may be preferred and more effective.

[1180] SNCR technologies convert NOx to molecular nitrogen via ammoniainjection into the furnace at about 1400-1800° F. However, excessammonia needs to be minimized to avoid conversion of SOx to ammoniumbisulfate, which deposits on downstream heat exchange

[1181] In conclusion, the present invention provides various mechanismsof environmental protection, if needed, far beyond what can be achievedwith most coals. As noted above, the present invention provides severalembodiments to address the concerns of environmental protection andcompliance. The optimization of these methods and embodiments can createa variety of control scenarios to address the specific needs(compliance, economic, etc.) of a particular combustion facility,existing or otherwise.

[1182] 11. Other Embodiments; General Issues

[1183] Finally, an additional embodiment of the present invention may beany combination of the above embodiments. Engineering factors willdetermine the optimal application for any of the above embodiments,separately or in combination. In any combination of the embodiments, thedegree required may be less than specified here due to the combinedeffects. Again, these concepts and embodiments may be applied to delayedcoking, Fluid Coking™, Flexicoking™ and other types of coking processes,available now or in the future.

[1184] In view of the foregoing disclosure, it may be within the abilityof one skilled in the relevant fields to make alterations to andsubstitutions in the present invention, without departing from thespirit of the invention as reflected in the appended claims.

Conclusion

[1185] Thus the production and use of the premium “fuel-grade” petroleumcoke, in the manner described in the present invention, provides asuperior solid fuel for conventional, coal-fired utility boilers andvarious other solid-fuel combustion applications. The environmentalcontrols of the present invention also provide unique technologyapplications with superior control capabilities.

[1186] While the above description contains many specificities, theseshould not be construed as limitations on the scope of the invention,but rather as an exemplification of the embodiments thereof. Forexample, other possible variations of the invention include thosebrought about through the substitution of equivalent components orprocess steps. Accordingly, the scope of the invention should bedetermined not by the embodiments illustrated, but by the appendedclaims and their legal equivalents, the appended claims hereby beingincorporated herein by reference.

What is claimed is:
 1. A process of producing a coke product, saidprocess comprising: providing a coke precursor material; subjecting saidcoke precursor material to a thermal cracking process; and maintainingthe ratio of asphaltic coke to thermal coke so as to promote theproduction of sponge coke; wherein said coke product is comprised ofsponge coke in an amount in the range of about 40% to 100% by weight. 2.The process of claim 1 wherein: said coke precursor material includes avolatile organic component; and said coke product has volatilecombustible materials (VCMs) present in an amount in the range of fromabout 13% to about 50% by weight.
 3. The process of claim 1 wherein theratio of asphaltic coke to thermal coke is maintained by controlling atleast one variable selected from the group consisting of coke precursormaterial characteristics, heater outlet temperature, coke drumtemperature, coke drum pressure, coker recycle rate, coke drum thermalquench, coke drum chemical reaction quench, and combinations thereof. 4.The process of claim 3 wherein said coke drum thermal quench, said cokedrum chemical reaction quench, or combinations thereof are added into acoke drum via injection systems selected from the group consisting of anexisting anti-foam injection system modified drill stem, an injectionlance at the top of the coke drum, and combinations thereof.
 5. Theprocess of claim 1 wherein said thermal cracking process is selectedfrom the group consisting of delayed coking, Flexicoking, and otherthermal cracking processes with by-product coke production.
 6. Theprocess of claim 1 wherein said coke product has porositycharacteristics suitable for adsorption use.
 7. The process of claim 6wherein the adsorption characteristics of said coke product are improvedby performing at least one step selected from the group consisting of:decreasing the ratio of asphaltic coke to thermal coke; including feedadditives in said coke precursor material that are adapted to releaselow molecular weight gases during said thermal cracking process;injecting low molecular weight gases into a coke mass in a coke drum atthe start of a decoking cycle of said thermal cracking process;hydroprocessing said coke product with sufficient hydrogen addition,temperature, pressure, catalyst activity, and residence time; treatingsaid coke product via chemical extraction of asphaltenes and resins withsufficient solvent, temperature, pressure, and residence time; treatingsaid coke product via chemical activation with sufficient chemicalactivator, temperature, pressure, and residence time; and combinationsthereof.
 8. The process of claim 6 further comprising impregnatingand/or adsorbing in said coke product at least one chemical compoundhaving desired combustion characteristics and/or characteristics thatotherwise enhance the fuel properties of said coke product.
 9. Theprocess of claim 8 wherein at least one volatile combustible material(VCM) is deposited via evaporation in said coke product and/or adsorbedin said coke product from a coke quench solution used in said thermalcracking process.
 10. The process of claim 8 wherein at least oneionizing agent is deposited via evaporation in said coke product and/oradsorbed in said coke product from a coke quench solution used in saidthermal cracking process.
 11. The process of claim 8 wherein at leastone oxygen-containing compound is deposited via evaporation in said cokeproduct and/or adsorbed in said coke product from a coke quench solutionused in said thermal cracking process.
 12. The process of claim 8wherein catalytic properties of said coke product are enhanced by thedeposition via evaporation in said coke product and/or adsorption insaid coke product of at least one catalyst or catalyst enhancementchemical from a coke quench solution used in said thermal crackingprocess.
 13. The process of claim 6 wherein said coke product hassufficient adsorption character to be used for at least one adsorptionapplication selected from the group consisting of solvent vaporrecovery, liquid purification, water purification, gas purification, airpurification, and flue gas cleanup.
 14. The process of claim 13 whereinsaid sponge coke has a honeycomb crystalline structure that is adaptedto provide low pressure drop in said at least one adsorptionapplication.
 15. The process of claim 14 wherein said coke product isadapted to be removed from a coke drum in at least one sectionsubstantially without destroying the integrity of said honeycombcrystalline structure.
 16. The process of claim 6 further comprisingadding at least one chemical compound to said coke product to enhanceadsorption characteristics of said coke product.
 17. The process ofclaim 16 wherein: at least one sulfur compound is added to said cokeproduct by a process selected from the group consisting of adsorptionand impregnation, wherein said at least one sulfur compound is adaptedto enhance the adsorption of mercury and/or another toxic chemical froma gas stream.
 18. The process of claim 1 further comprising adding tosaid coke precursor material at least one component selected from thegroup consisting of plastics, rubbers, and similar materials.
 19. Theprocess of claim 18 wherein said at least one component is added to saidcoke precursor material downstream of a feed heater via at least onesystem selected from the group consisting of grinding systems,pulverizing systems, and extruder injection systems.
 20. The process ofclaim 6 further comprising adding at least one chemical compound to saidcoke product to enhance catalyst activity and properties of said cokeproduct.
 21. A coking process comprising: providing a coke drumcontaining a coke mass and a vapor phase above said coke mass; andinjecting a quench medium in said vapor phase during a coking cycle;whereby thermal cracking in said vapor phase is quenched during saidcoking cycle.
 22. The coking process of claim 21 wherein said thermalcracking is inhibited by a quench selected from the group consisting ofa thermal quench, chemical reaction quench, and combinations thereof.23. The process of claim 21 wherein: said quench medium is selected froma group consisting of hydrogen, coker gas oil, and combinations thereof;and said quench medium is injected via a modified drill stem positionedin said coke drum during said coking cycle and maintained at a levelabout 0.5 to about 10 feet above said coke mass.
 24. A process forremoving sulfur from petroleum coke, said process comprising: adding atleast one sulfur reagent to said petroleum coke; and combusting saidpetroleum coke such that said at least one sulfur reagent reacts withsulfur in said petroleum coke to form solid particles; wherein saidsolid particles are adapted to be collected.
 25. The process of claim 24wherein: at least one sulfur reagent is added to said coke product by aprocess selected from the group consisting of adsorption andimpregnation
 26. The process of claim 24 wherein: said at least onesulfur reagent includes a compound comprising a component selected fromthe group consisting of earth metals and alkaline earth metals.
 27. Theprocess of claim 25 wherein said at least one sulfur reagent is added tosaid petroleum coke by adsorption from a coke quench solution during acoking process.
 28. The process of claim 26 wherein said at least onesulfur reagent is selected from the group consisting of calcitichydrates and dolomitic hydrates.
 29. A delayed coking process forproducing a coke product, said process comprising: adding to a cokeprecursor material at least one component selected from the groupconsisting of plastics, rubbers, coal, wood, cardboard, paper,cellulosic materials, and similar materials; wherein said at least onecomponent is adapted to provide a benefit selected from the groupconsisting of improved coke product yields, enhanced coke productadsorption character, and an alternative use (or recycle) of said atleast one component.
 30. A process of hydroprocessing coke, said processcomprising: providing a coke material comprising bonded chemicalcomponents from the group consisting of asphaltenes, resins, andcondensed/polymerized aromatics; and subjecting said coke material tochemical reactions from the group consisting of hydrogenation reactions,hydrogenolysis reactions, and cracking reactions via sufficient time,temperature, pressure, hydrogen, and catalyst activity to promotecracking and saturation of said coke material wherein said coke materialproduces cracked hydrocarbons and residual coke.
 31. The process ofclaim 30 wherein said residual coke has at least one characteristicselected from the group consisting of greater porosity, less coke mass,and lower content of heterocyclic compounds than said coke material. 32.The process of claim 31 wherein said heterocyclic compounds are selectedfrom the group consisting of sulfur, nitrogen, oxygen, and metals. 33.The process of claim 30 wherein said hydrogenation reactions, saidhydrogenolysis reactions, and said cracking reactions are simultaneous.34. The process of claim 30 wherein said coke material has sufficientporosity and internal surface area to provide said catalyst activity.35. The process of claim 30 wherein solid-gas phase reactionssufficiently transfer hydrogen free-radicals in said hydrogenationreactions, said hydrogenolysis reactions, and said cracking reactions toreduce hydrogen partial pressure requirements of solid-liquid-gas phasereactions.
 36. The process of claim 30 wherein said coke material isderived from crude oil.
 37. The process of claim 36 wherein said processis promoted in a delayed coking process between a coking cycle and adecoking cycle.
 38. The process of claim 37 wherein said delayed cokingprocess utilizes at least 3 coke drums and at least 3 process cycles.39. The process of claim 37 further comprising hydrotreating liquidhydrocarbons in at least one time period selected from the groupconsisting of before said process and after said process.
 40. A processof treating coke, said process comprising: providing a coke materialcomprising at least one component selected from the group consisting ofasphaltenes, resins, and condensed/polymerized aromatics; subjectingsaid coke material to at least one chemical extraction reaction viasufficient solvent residence time, temperature, pressure, and catalyticactivity to promote the removal of said at least one component from saidcoke material and to produce a residual coke with greater porosity thansaid coke material.
 41. The process of claim 40 wherein said at leastone chemical extraction reaction is controlled to promote pore sizessuitable for predetermined adsorption applications.
 42. The process ofclaim 40 wherein the removal of said at least one component from saidcoke material is promoted in a delayed coking process between a cokingcycle and a decoking cycle.
 43. The process of claim 42 wherein saiddelayed coking process utilizes at least 3 coke drums and at least 3process cycles.
 44. A process of treating coke, said coke comprising:providing a coke material comprising a porous, carbonaceous content; andsubjecting said coke material to at least one chemical carbonizationreaction via sufficient chemical activator, residence time, temperature,pressure, and catalytic activity to produce a residual coke with greaterporosity than said coke material.
 45. The process of claim 44 whereinsaid at least one carbonization reaction is controlled to promote poresizes suitable for predetermined adsorption applications.
 46. Theprocess of claim 44 wherein said at least one chemical carbonizationreaction is promoted in a delayed coking process between a coking cycleand a decoking cycle.
 47. The process of claim 46 wherein said delayedcoking process utilizes at least 3 coke drums and at least 3 processcycles.